TWI445294B - Switching power converter and method thereof - Google Patents

Description

Switching power converter and its operation method

The present invention relates to switched power converters, and more particularly to switching signal frequency control for switched power converters.

Consumer electronics are becoming more and more demanding in terms of size, weight and power consumption, which makes small, lightweight, and highly efficient switching power converters more popular than linear rectifiers. Figure 1 is a schematic diagram of a conventional switched power converter. The switching power converter 100 includes a switch SW, a storage inductor L, a diode D, a voltage stabilizing capacitor C, and a switching signal generator 110. A switching signal generator 110 compares the load R _L of the cross voltage V ₂ and a reference voltage V _ref to generate a switching signal for controlling the switch SW is turned on or off, when the switch SW is turned on, diode D is off, the first power supply V ₁ Charging the energy storage inductor L, that is, the energy storage inductor L stores the energy of the first power source; on the other hand, when the switch SW is turned off, the current i _L stored on the energy storage inductor L turns on the diode D, and The second power supply V ₂ supplies power to the voltage stabilizing capacitor C and the load R _L . The ratio of the first power source V ₁ to the second power source V _{2 is related to} the ratio of the on-time and the off-time of the switch SW, that is, related to the duty ratio of the switching signal, assuming that the first power source V ₁ is a certain voltage source, When the load R _{L is} fixed and the duty cycle of the switching signal is also fixed, the proportional relationship between the first power source V ₁ and the second power source V ₂ is also fixed, and the second power source V ₂ is a certain value. However, in practical applications, the load R _L may change at any time. When the load R _L changes to a larger load and consumes more energy, the voltage value of the second power source V ₂ may also decrease, in order to maintain the second power source V ₂ at a certain value, switching The signal generating circuit 110 changes the duty cycle of the switching signal according to the reference voltage V _ref and the second power source V ₂ , so that more energy is transmitted from the first power source V ₁ to the load R _L , and the second power source is maintained at a certain value. . Such a switching signal generation method is a conventional pulse width modulation method.

Similarly, when the load R _L becomes a small load and consumes less energy, the switching signal generating circuit 110 also reduces the pulse width of the switching signal so that less energy is transmitted from the first power source V _{1 .} Up to the load R _L , however, there is still a certain limit to the narrowest pulse width that the switching signal generating circuit 110 can generate. When the switching signal generating circuit 110 has supplied its switching signal of the narrowest pulse width, excessive energy is still transmitted to Load R _L , at this time, the switching signal generating circuit will increase the spacing between each pulse wave (reducing the frequency of the switching signal), that is, the switching signal is generated by a conventional pulse frequency modulation method to obtain a more The energy delivered to the load R _{L is} further reduced so that the second power source V ₂ is maintained at a certain value.

The switching signal generated by the pulse frequency modulation mode may become the power supply noise affecting the load operation as the second power source V ₂ enters the load R _L , for example, the load R _L is an audio circuit, and when the signal is switched When the frequency is between 20KHz and 0KHz, the user of the audio circuit may hear switching noise originating from the switching signal.

In order to avoid the above problems, it is an object of the present invention to provide a switching power converter and a method of operating the same by controlling the magnitude of the current input to the energy storage element to avoid switching signals falling into a particular frequency.

In accordance with an embodiment of the present invention, a switched power converter is provided. The switching power converter converts a first power source into a second power source according to a switching signal, and includes an energy storage component and a current controller. The energy storage component stores energy of one of the first power sources and releases the energy in the form of the second power source; and the current controller is electrically connected to the energy storage component for selectively enabling the switching signal according to the switching signal The first power source is coupled to the energy storage component, and adjusts a frequency of one of the energy storage elements from the first power source according to a switching frequency of the switching signal.

In accordance with an embodiment of the present invention, a method of operating the above described switched power converter is provided. The method includes storing energy of one of the first power sources by an energy storage component and releasing the energy in the form of the second power source; selectively coupling the first power source to the energy storage component according to the switching signal; One of the switching signals switches a frequency to adjust a current value of one of the energy storage elements from the first power source.

2 is a schematic diagram of a switched power converter in accordance with an embodiment of the present invention. The switched power converter 200 includes a current controller 220, a storage inductor L, a diode D, a voltage stabilizing capacitor C, and a switching signal generator 210. Please note that for the sake of brevity, only the circuit components related to the present invention are shown in FIG. In addition, the circuit configuration of the switched power converter shown in FIG. 2 is for illustrative purposes only, and the present invention should not be limited to this circuit configuration. Those skilled in the art will be able to store under the teachings of the present invention. The energy can be replaced by other energy storage components (such as energy storage capacitors), or combined with buck converters, boost converters, flyback converters, and the like. Switched DC power converters are used to design various switching power converters, and the various variations described above are also within the scope of the present invention.

3 is a flow chart of a method of operating a switched power converter in accordance with an embodiment of the present invention. The method of operating a switched power converter includes a plurality of steps, which are listed below: Step 310: Storing one of the first power sources with an energy storage component and releasing the energy in the form of a second power source.

Step 320: selectively coupling the first power source to the energy storage component according to the switching signal.

Step 330: Adjust a current value of one of the energy storage elements from the first power source according to one of the switching signals.

If substantially the same result can be achieved, the steps of the above method are not necessarily performed in the order shown, and need not be continuous, that is, other steps may be inserted, or any of the above steps may be exchanged or omitted. Various changes in the above steps (i.e., the steps shown in Fig. 3) are considered to fall within the scope of the present invention.

The switching power converter 200 converts a first power source V ₁ into a voltage value different from the second power source V _{2 of the} first power source V ₁ according to a switching signal S _SW . In this embodiment, the first power source V ₁ and the second power source V ₂ are DC power sources having different voltage values, and according to step 310, the energy storage inductor L stores one of the first power sources V ₁ and the second power source V The form of ₂ releases energy. The switching signal generator 210 generates the switching signal S _SW according to a reference voltage V _ref and the second power source V ₂ in a pulse frequency modulation manner. The current controller 220 is electrically connected to the energy storage inductor L and the switching signal S _SW generator 210. According to step 320, the current controller 220 is configured to selectively couple the first power source to the memory according to the switching signal S _{SW .} The inductor L can establish an electrical connection path between the first power source V ₁ and the energy storage inductor L, so that the energy storage inductor L can store the energy of the first power source V ₁ .

As described above, when the load R _{L is} changed, in order to maintain the second power source V ₂ at a certain value, the switching signal generator 210 changes the frequency of the switching signal S _SW to change the energy transmitted from the first power source V ₁ , However, in order to prevent the switching signal S _{SW from} falling into certain frequency ranges and causing switching noise to affect the normal operation of other circuits, the switching signal S _SW may be changed from the first power source V ₁ before falling into certain frequency ranges. magnitude of the input current storage element, energy transfer from the first to change the power source V _1, V ₂ of the second power supply still have to be maintained at a constant value. According to step 330, the current controller 220 adjusts the value of the current i _L input to the one of the energy storage elements from the first power source V ₁ according to the switching frequency of one of the switching signals S _SW . Those skilled in the art can design a variety of different current controllers 220, which are detailed in the following two examples.

Figure 4 is a schematic illustration of one embodiment of a switched power converter of the present invention and the internal structure of its current controller. It should be noted that FIG. 4 differs from FIG. 2 in that FIG. 4 discloses the internal structure of the power supply controller 220. Therefore, for the sake of brevity, the same as in FIG. 2 will not be described again. In this embodiment, the power controller 220 includes a frequency detector 222, a demultiplexer 224, and a plurality of switches SW1, SW2, and SW3. The number and connection of the switches in FIG. 4 are for illustrative purposes only and should not be construed as limiting the invention. Those skilled in the art can design a plurality of switches of different numbers and connections according to their needs.

In order to prevent the frequency of the switching signal from falling into certain specific frequency ranges and affecting the normal operation of other circuits, the frequency detector 222 generates a switch selection signal S _C according to the switching frequency of the switching signal S _SW to control the output of the demultiplexer 224. Switch signal S _SW to the appropriate switch. For example, the switches SW1, SW2, and SW3 have on-resistances R1, R2, and R3, respectively (R1 > R2 > R3), and when the frequency detector 222 detects that the switching frequency is greater than 20 kHz and less than 100 kHz, the frequency detector 222 outputs a switch. The signal S _{C is} selected to the demultiplexer 224, so that the demultiplexer 224 outputs the switching signal S _{SW to} control the on and off of the switch SW2. When the switch SW2 is turned on, the first power source V ₁ stores energy to the energy storage through the switch SW2. The inductance L, and when the switch SW2 is turned off, the energy storage inductor L releases energy in the form of the second power source V ₂ .

Assuming that the load R _{L is} gradually changed to a light load, in order to maintain the second power source V ₂ at a certain value, the switching signal generator 210 gradually reduces the switching frequency of the switching signal S _SW to reduce the energy transmitted from the first power source V ₁ . When the frequency detector 222 detects that the switching frequency is about 20 kHz, the frequency detector 222 outputs the switch selection signal S _C to the demultiplexer 224 to cause the demultiplexer 224 to output the switching signal S _{SW to} selectively control the switch SW1. When the switch is turned on or off, the first power source V ₁ can store energy to the storage inductor L through the switch SW1 when the switch SW1 is turned on. Since the on-resistance R1 of the switch SW1 is greater than the on-resistance R2 of the switch SW2, the current i _L flowing into the storage inductor L is reduced, thereby reducing the energy transmitted from the first power source V ₁ , so the switching frequency will not be reduced anymore. The second power source is still maintained at a certain value. Similarly, when the load R _{L is} changed to a heavy load, in order to avoid the switching frequency being greater than 100 kHz, the switch SW3 with a small on-resistance is selectively electrically connected to the first power source V ₁ and the energy storage inductor L. In order to improve the energy conversion efficiency, a plurality of switches (for example, switches SW3 and SW2) can be turned on at the same time to reduce the equivalent impedance of the switch as a whole and reduce the energy consumed on the switch.

Fig. 5 is a schematic view showing another embodiment of the switching power converter of the present invention and its internal structure of the current controller. It is to be noted that FIG. 5 differs from FIG. 4 in that FIG. 5 discloses another internal structure for realizing the power supply controller 220. Therefore, for the sake of brevity, the same as in FIG. 4 will not be described again. In this embodiment, the power controller 220 includes a frequency detector 226, a voltage regulator 228, and a switch SW. The frequency detector 226 generates a voltage adjustment signal S _V according to the switching frequency of the switching signal S _SW , and the voltage regulator 228 is electrically connected to the frequency detector and the switch SW for adjusting the switching signal S according to the voltage adjustment signal S _{V .} The voltage value of _SW is used to generate an adjusted switching signal S _SW ' to adjust the on-resistance of the switch, and the switch SW is configured to selectively electrically connect the first power source V ₁ according to the adjusted switching signal S _SW ' Connected to the energy storage inductor L.

In this embodiment, in order to prevent the switching frequency of the switching signal S _SW from falling into a certain range and affecting the normal operation of other circuits, the adjusted switching signal S _SW ' having different voltage values is used to control the conduction when the switch SW is turned on. impedance to thereby change the amount of energy transferred from the first power source V _1. The switch SW can be a conventional field effect transistor (FET), a bipolar junction transistor (BJT) or any switching element that can vary its on-resistance using the magnitude of the switching voltage. Fig. 6 is a waveform diagram of the adjusted switching signal S _SW ' having different voltage values. For example, when the switching frequency is greater than 20KHz and less than 100KHz, the frequency detector 226 outputs the voltage adjustment signal S _V so that the voltage regulator 228 does not perform voltage adjustment on the switching signal S _SW , that is, the switching signal S _SW0 ' output by the voltage regulator 228 . It is the same as the switching signal S _SW originally outputted by the switching signal generator 210 (0V~2.5V). When the load R _L changes to a heavy load and the switching frequency is about 100KHz, the frequency detector 226 outputs the voltage adjustment signal S _{V to} cause the voltage regulator 228 to perform voltage adjustment on the switching signal S _SW , so that the output of the voltage regulator 228 has a comparison. The high-on-voltage switching signal S _SW1 '(0V~2.8V), at this time, the switch SW is controlled by the switching signal S _SW1 ' having a higher voltage, and thus has a lower on-resistance when turned on, so that the first The power supply V _{1 is} able to deliver more energy, so that the switching frequency will no longer increase. Similarly, when the load R _L changes to a light load and the switching frequency is about 20 kHz, the frequency detector 226 outputs a voltage adjustment signal S _{V to} cause the voltage regulator 228 to perform voltage adjustment on the switching signal S _SW to cause the voltage regulator 228 outputs a switching signal S _SW2 ' (0V~2.3V) having a lower turn-on voltage. At this time, the switch SW is controlled by the switching signal S _SW2 ' having a lower voltage, and thus has a higher on-resistance when turned on. So that the first power source V ₁ only transmits less energy, and as a result, the switching frequency will no longer decrease. Please note that the above-mentioned on-voltage values (2.5V, 2.8V, 2.3V) are for illustrative purposes only and should not be construed as limiting the invention. Those skilled in the art will be able to design various types depending on the characteristics of the various switches. Different turn-on voltage values.

In addition, those skilled in the art can also use the technique of controlling a plurality of switches (such as the embodiment corresponding to FIG. 4) and the technique of controlling the on-voltage of the switch (such as the embodiment corresponding to FIG. 5) to change the transmission from the first The energy of a power source to avoid the switching frequency falling into an inappropriate frequency range, which will not be described here.

In summary, according to the apparatus and method provided by the embodiment of the present invention, the energy transmitted from the first power source can be changed by adjusting the current magnitude of the input energy storage component from the first power source, so that the switching frequency of the switching power converter is changed. Will not fall into certain frequency ranges and affect the normal operation of other circuits.

The above are only the embodiments of the present invention, and all changes and modifications made by the scope of the present invention should be within the scope of the present invention.

100, 200. . . Switching power converter

110, 210. . . Switching signal generator

220. . . Current controller

222, 226. . . Frequency detector

224. . . Demultiplexer

228. . . Voltage regulator

Figure 1 is a schematic diagram of a conventional switched power converter.

Figure 2 is a schematic illustration of one embodiment of a switched power converter in accordance with the present invention.

3 is a flow chart of a method of operating a switched power converter in accordance with an embodiment of the present invention.

Figure 4 is a schematic illustration of one embodiment of a switched power converter of the present invention and the internal structure of its current controller.

Fig. 5 is a schematic view showing another embodiment of the switching power converter of the present invention and its internal structure of the current controller.

Figure 6 is a waveform diagram of the adjusted switching signal with different voltage values.

200. . . Switching power converter

210. . . Switching signal generator

220. . . Current controller

Claims (16)

A switching power converter converts a first power source into a second power source according to a switching signal, comprising: an energy storage component, storing energy of one of the first power sources and releasing the energy in the form of the second power source; And a current controller electrically connected to the energy storage component for selectively coupling the first power source to the energy storage component according to the switching signal, and adjusting the frequency according to one of the switching signals The first power source inputs a current value of the energy storage element, and the current controller includes a frequency detector, wherein the frequency detector is configured to detect the switching frequency of the switching signal, and the frequency detector detects that the switching frequency is about to When falling within a specific frequency range, the current controller adjusts the current value input from the first power source to the energy storage component such that the switching frequency does not fall within the specific frequency range. The switching power converter of claim 1, wherein the frequency detector generates a voltage adjustment signal according to the switching frequency, and the current controller further comprises: a switch for using the adjusted switching signal Optionally electrically connecting the first power source to the energy storage component; and a voltage regulator electrically connected to the frequency detector and the switch, configured to adjust a voltage value of the switching signal according to the voltage adjustment signal The adjusted switching signal is generated to adjust the on-resistance of the switch. The switching power converter of claim 2, wherein when the switching frequency is lower than a predetermined frequency, the frequency detector outputs the voltage adjustment signal to the voltage regulator to increase the conduction resistance of the switch. . The switching power converter of claim 1, wherein the frequency detector generates a switch selection signal according to the switching frequency, and the current controller further comprises: a plurality of switches; and a demultiplexer, the electric Connected to the frequency detector and the plurality of switches, selectively outputting the switching signal to at least one of the plurality of switches according to the switch selection signal; wherein the at least one switch selectively connects the first switch according to the switching signal A power source and the energy storage component. The switching power converter of claim 4, wherein when the switching frequency is lower than a predetermined frequency, the frequency detector outputs the switch selection signal to the demultiplexer to correspond to the plurality of switches One of the equivalent on-resistances increases. The switching power converter of claim 1, wherein the first power source and the second power source are both DC power sources. The switching power converter of claim 1, wherein the switching signal is generated according to a pulse frequency modulation according to a voltage value of the second power source. The switching power converter of claim 1, wherein the voltage value of the second power source is different from the voltage value of the first power source. An operating method for a switching power converter, wherein the switching power converter converts a first power source into a second power source according to a switching signal, the method comprising: storing the first power source by using an energy storage component One of the energy releases the energy in the form of the second power source; selectively coupling the first power source to the energy storage element according to the switching signal; and detecting a switching frequency of the switching signal by using a frequency detector; And detecting that the switching frequency is about to fall within a specific frequency range, adjusting a current value of the one of the energy storage elements from the first power source according to one of the switching signals, so that the switching frequency does not fall into the specific Frequency Range. The method of claim 9, wherein the voltage value of the second power source is different from the voltage value of the first power source. The method of claim 9, wherein the step of adjusting the current value of the first power source to the energy storage element according to the switching frequency of the switching signal comprises: generating a voltage adjustment signal according to the switching frequency; Adjusting a switching signal to selectively electrically connect the first power source to the energy storage component; Adjusting the voltage value of the switching signal according to the voltage adjustment signal to generate the adjusted switching signal to adjust the on-resistance of the switch. The method of claim 11, wherein when the switching frequency is lower than a predetermined frequency, the voltage adjustment signal is output to increase the on-resistance of the switch. The method of claim 9, wherein the step of adjusting the current value of the first power source to the energy storage element according to the switching frequency of the switching signal comprises: generating a switch selection signal according to the switching frequency; The switch selection signal selectively outputs the switching signal to at least one of the plurality of switches; wherein the at least one switch selectively connects the first power source and the energy storage element according to the switching signal. The method of claim 13, wherein when the switching frequency is lower than a predetermined frequency, the switch selection signal is output to increase an equivalent on-resistance of the plurality of switches. The method of claim 9, wherein the first power source and the second power source are both DC power sources. The method of claim 9, wherein the switching signal is generated according to a pulse frequency modulation according to a voltage value of the second power source.