Power supply voltage control circuit and control method thereof

Abstract

According to the power supply voltage control circuit, a charging control circuit is adopted, an input power supply is used for charging a power supply capacitor, or when the output voltage of a voltage conversion circuit is low, the charging control circuit is used for charging the power supply capacitor, and when the output voltage of the voltage conversion circuit is high, an auxiliary winding is used for charging the power supply capacitor. Therefore, the problems of high voltage withstanding requirement of the voltage conversion control chip and large circuit loss caused by the wide output voltage range of the voltage conversion circuit are avoided.

Description

Technical Field

[0001] Embodiments of the present invention relate to electronic circuits, and more particularly, to a power supply voltage control circuit. Background Art

[0002] As the functions of smartphones increase, power consumption becomes faster and faster, and fast charging technology comes into being. Figure 1 FIG. 1 shows an existing voltage conversion circuit 10 for a fast charging power supply. Figure 1 As shown, the AC voltage Vac is provided to the transformer T1 of the voltage conversion circuit 10 with a DC voltage Vbus after passing through the rectifier bridge circuit 101. The voltage conversion control chip 102 controls the duty cycle of the primary switch M1 coupled to the transformer T1 to control the primary-to-secondary energy conversion of the transformer T1, thereby controlling the output voltage Vout. The voltage conversion control chip 102 is powered by the auxiliary winding Lt. The power supply voltage Vcc provided by the auxiliary winding Lt is proportional to the output voltage Vout, and the proportionality coefficient is determined by the turns ratio of the auxiliary winding Lt and the secondary winding Ls, that is, Vcc:Vout=N(Lt):N(Ls), where N represents the number of turns of the winding. It should be understood that in order to maintain the normal operation of the voltage conversion control chip 102, the power supply voltage Vcc has a minimum voltage limit, usually around 10V. When the output voltage Vout has a larger range, for example, from 3.3V to 20V, in order to make the power supply voltage Vcc still reach the minimum voltage requirement when the output voltage Vout = 3.3V, the turns ratio of the auxiliary winding Lt to the secondary winding Ls must be at least 3:1. When the turns ratio of the auxiliary winding Lt to the secondary winding Ls is 3:1, when the output voltage Vout = 20V, the power supply voltage Vcc is 60V. This results in a relatively high withstand voltage requirement for the voltage conversion control chip 102, and the power loss will also be very large. Summary of the invention

[0003] In order to solve the above technical problems, an embodiment of the present invention provides a power supply voltage control circuit, which uses the input power supply to charge the power supply capacitor when the input voltage of the voltage conversion circuit is low. At the same time, the power supply voltage control circuit and the auxiliary winding can be combined, and when the output voltage of the voltage conversion circuit is low, the power supply capacitor is charged by the power supply voltage control circuit and the input power supply, and when the output voltage is high, the power supply capacitor is charged by the auxiliary winding, thereby avoiding the problem of high voltage resistance requirements and large circuit loss of the voltage conversion control chip caused by the wide output voltage range of the voltage conversion circuit.

[0004] According to an embodiment of the present invention, a power supply voltage control circuit is proposed, comprising: a charging control circuit, which outputs a charging control signal based on an input voltage and a power supply voltage; and a charging current source, which is coupled to the input voltage and has a control terminal for receiving the charging control signal and providing a charging current under the control of the charging control signal; wherein, within a charging window, after a set time period has passed since the starting point of the charging window, the charging control signal controls the charging current source to provide a charging current, and when the power supply voltage rises to a charging stop reference, the charging control signal controls the charging current source to stop providing a charging current.

[0005] In some embodiments, the charging window takes the lowest point of the input voltage as the midpoint and is symmetrically distributed on both sides of the lowest point of the input voltage.

[0006] According to an embodiment of the present invention, a power supply circuit is also proposed, including the aforementioned power supply voltage control circuit, and also including a power supply capacitor having a charging end coupled to a charging current source and a grounding end coupled to a reference ground.

[0007] According to an embodiment of the present invention, a voltage conversion circuit is also proposed, including the aforementioned power supply circuit, and also including: a transformer having a primary winding and a secondary winding; a primary switch coupled to the primary winding; and a voltage conversion control chip, outputting a primary control signal to the control end of the primary switch to control the on and off of the primary switch.

[0008] In some embodiments, the transformer further includes an auxiliary winding, and the auxiliary winding is coupled to the charging end of the power capacitor through a diode.

[0009] According to an embodiment of the present invention, a power capacitor charging control method is also proposed, including: within a charging window, after a preset time period has passed from the starting point of the charging window, controlling a charging current source to provide a charging current to the power capacitor to generate a power voltage on the power capacitor; and when the power voltage is greater than a charging stop reference, controlling the charging current source to stop providing the charging current; wherein the charging window takes the lowest point of the input voltage as the midpoint and is symmetrically distributed on both sides of the lowest point of the input voltage.

[0010] In some embodiments, the aforementioned power capacitor charging control method further includes: when the power supply voltage is less than a leakage charging reference, controlling the leakage current source to provide leakage current; and when the power supply voltage is greater than a leakage stop reference, controlling the leakage current source to stop providing leakage current. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to better understand the present invention, the present invention will be described in detail according to the following drawings:

[0012] Figure 1 An existing voltage conversion circuit 10 for a fast charging power source is shown;

[0013] Figure 2 FIG. 2 shows a schematic diagram of a circuit structure of a voltage conversion circuit 20 according to an embodiment of the present invention;

[0014] Figure 3 A schematic flow chart of a working method 30 of an input voltage control circuit 231 according to an embodiment of the present invention is shown;

[0015] Figure 4 FIG. 2 is a schematic diagram showing waveforms of various signals of the charging control circuit 23 according to an embodiment of the present invention;

[0016] Figure 5 FIG. 5 shows a schematic diagram of a circuit structure of a voltage conversion circuit 50 according to an embodiment of the present invention;

[0017] Figure 6 FIG. 4 shows a circuit structure diagram of a voltage conversion circuit 60 according to an embodiment of the present invention;

[0018] Figure 7 FIG. 4 is a schematic diagram showing a circuit structure of a voltage conversion circuit 70 according to an embodiment of the present invention;

[0019] Figure 8 FIG. 8 is a flow chart of a power supply capacitor charging control method 80 according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that these specific details do not have to be used to implement the present invention. In other examples, in order to avoid confusing the present invention, known circuits, materials or methods are not specifically described.

[0021] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment," "in an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any appropriate combination and / or sub-combination. In addition, it will be appreciated by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale. The same reference numerals indicate the same elements. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] Figure 2 The circuit structure schematic diagram of the voltage conversion circuit 20 according to an embodiment of the present invention is shown. The voltage conversion circuit 20 includes rectifier circuits 24 and 25, a transformer T1, a primary switch M1, a secondary switch Ds, a voltage conversion control chip 21 and a power supply voltage control circuit 22. The rectifier circuit 24 rectifies the AC voltage output by the AC power supply Vac into a DC voltage Vbus and provides it to the transformer T1. The transformer T1 has a primary winding Lp and a secondary winding Ls. The primary switch M1 is coupled to the primary winding Lp. The secondary switch Ds is coupled to the secondary winding Ls. The voltage conversion control chip 21 outputs a primary control signal G1 to the control end of the primary switch M1 to control the on and off of the primary switch M1. Specifically, when the primary switch M1 is turned on, the secondary switch Ds is turned off, the current flowing through the primary winding Lp increases, the primary winding Lp stores energy, and the output capacitor Co supplies power to the load. When the primary switch M1 is turned off, the secondary switch Ds is turned on, and the energy of the primary winding Lp is transferred to the secondary winding Ls. The secondary winding Ls supplies power to the load and charges the output capacitor Co to maintain the output voltage Vout. The rectifier circuit 25 rectifies the AC voltage output by the AC power source Vac into an input voltage Vin with a half-sine wave waveform. The power supply voltage control circuit 22 receives the input voltage Vin and outputs a power supply voltage Vcc for powering the voltage conversion control chip 21.

[0023] In some embodiments, the rectifier circuit 24 includes a rectifier bridge and a filter capacitor, and the rectifier circuit 25 includes a rectifier bridge.

[0024] like Figure 2 As shown, the power supply voltage control circuit 22 includes a power supply capacitor Cvcc, a charging current source Is and a charging control circuit 23. The power supply capacitor Cvcc has a charging terminal coupled to the charging current source Is, and has a ground terminal coupled to the reference ground PGND. The charging control circuit 23 outputs a charging control signal Gc to the charging current source Is, controls the charging current source Is to charge the power supply capacitor Cvcc, forms a power supply voltage Vcc thereon, and supplies power to the voltage conversion control chip 21.

[0025] exist Figure 2 In the embodiment, the charging control circuit 23 includes an input voltage control circuit 231, a power supply voltage comparison circuit 232 and a charging control logic circuit 233. The input voltage control circuit 231 receives an input voltage Vin and a charging stop signal Rd, and provides a charging setting signal Sc. The power supply voltage comparison circuit 232 receives a power supply voltage Vcc and a charging stop reference Vccd, and outputs a charging stop signal Rd. The charging control logic circuit 233 receives a charging setting signal Sc and a charging stop signal Rd, and outputs a charging control signal Gc to control a charging current source Is. Figure 2In an embodiment, the charging control logic circuit 233 includes an RS trigger FF1. The set end of the RS trigger FF1 receives a charging set signal Sc, the reset end receives a charging stop signal Rd, and the output end outputs a charging control signal Gc. Wherein, within the charging window, after a set time period has passed from the starting point of the charging window Cw, the charging control signal Gc controls the charging current source Is to provide a charging current to charge the power supply capacitor Cvcc. When the power supply voltage Vcc reaches the charging stop reference Vccd, the charging control signal Gc controls the charging current source Is to stop charging the power supply capacitor Cvcc. The charging window Cw is a window symmetrical based on the minimum value of the input voltage Vin. In some embodiments, the value of the input voltage Vin drops to the charging window threshold Vr as the starting point of the charging window Cw, and the input voltage Vin drops to the minimum value (e.g., zero) and then rises to the charging window threshold Vr again as the end point of the charging window Cw.

[0026] The input voltage control circuit 231 can be implemented by using a digital circuit, that is, a digital description language is used to describe the working method and process of the input voltage control circuit 231, and then the circuit is automatically generated. Figure 3 FIG. 2 is a flow chart showing a working method 30 of the input voltage control circuit 231 according to an embodiment of the present invention. Figure 3 As shown, the working method 30 includes: step 301, detecting the input voltage Vin; step 302, determining the charging window Cw based on the input voltage Vin; step 303, within the charging window Cw, after the set time Ts at the starting point of the charging window Cw, the charging control signal Gc controls the charging current source Is to provide the charging current; and step 304, when the power supply voltage Vcc rises to the charging stop reference Vccd, the charging control signal Gc controls the charging current source Is to stop providing the charging current. The charging current source Is is controlled to start providing the charging current and stop providing the charging current as a charging cycle.

[0027] There is no order relationship for the implementation of the steps of the above working method 30.

[0028] The input voltage Vin is a sine half wave after rectification of the AC voltage Vac, and the period of the input voltage Vin is half of the AC voltage Vac, and the frequency is twice that of the AC voltage Vac. When the AC voltage Vac is determined, the peak value of the input voltage Vin is also fixed. In step 302 of an embodiment of the present invention, the peak value of the input voltage Vin determines the width of the charging window Cw. In one embodiment, when the peak value of the input voltage Vin is 100V, the charging window threshold Vr is 10V, and the width of the charging window Cw is the time when the input voltage Vin drops to 10V and rises to 10V again. A higher charging window threshold Vr may result in lower circuit efficiency, and a lower charging window threshold Vr may result in failure to provide sufficient power supply voltage Vcc in time. A person of ordinary skill in the art may set the charging window threshold according to application requirements and circuit parameters. For example, when the peak value of the input voltage Vin is 100V, the charging window threshold may also be set to 15V or 20V.

[0029] In some embodiments, the value of the charging window threshold Vr is a fixed value, for example, the value of the charging window threshold Vr can be fixed to 10 V. In this case, when the frequency of the input voltage Vin remains unchanged, the higher the peak value of the input voltage Vin, the narrower the charging window Cw, and the lower the peak value of the input voltage Vin, the wider the charging window Cw.

[0030] In some embodiments, the value of the charging window threshold Vr is proportional to the peak value of the input voltage Vin. In this case, if the input voltage Vin is a half-sine wave, the width of the charging window Cw is related to the frequency of the input voltage Vin, but has nothing to do with the magnitude of the input voltage Vin. If Vr = 0.7Vin_pk, the window width of the charging window Cw is approximately Tin / 2, where Vin_pk is the peak value of the input voltage Vin, and Tin is the period of the input voltage Vin with a half-sine wave.

[0031] In some embodiments, the value of the charging window threshold Vr can be adjusted according to the peak value of the input voltage Vin. For example, when the peak value of the input voltage Vin exceeds 100V, the charging window threshold Vr is fixed at 50V, and when the peak value of the input voltage Vin is less than 100V, the value of the charging window threshold Vr is proportional to the peak value of the input voltage Vin, for example, Vr = 0.5Vin_pk.

[0032] In one embodiment, when the frequency of the input voltage Vin is the same, the larger the value of the input voltage Vin is, the higher the charging window threshold Vr is, and the wider the charging window Cw is. Conversely, the lower the charging window threshold Vr is, the narrower the charging window Cw is.

[0033] In one embodiment, the set duration Ts is obtained based on the first duration T1 and the second duration T2 in the previous charging window. The first duration T1 in the previous charging window is the duration from the window start point in the previous charging window to the time when the charging current source Is starts to provide the charging current, and the second duration T2 in the previous charging window is the duration from the time when the charging current source Is stops providing the charging current in the previous charging window to the end point of the charging window. That is, the first duration T1 in the current charging window is the preset duration Ts obtained based on the first duration T1 and the second duration T2 in the previous charging window.

[0034] The power supply voltage comparison circuit 232 may be a comparator. In one embodiment, when the power supply voltage Vcc is higher than the charge stop reference Vccd, the charge stop signal Rd is valid. It should be understood that any circuit that can generate a valid signal indicating that the power supply voltage Vcc rises to the charge stop reference Vccd can be used as a power supply voltage comparison circuit.

[0035] The valid state of a signal may be a level state, such as a high level, and the invalid state may be another level state, such as a low level. It may also be just the opposite, that is, a low level characterizes the valid state of a signal, and a high level characterizes the invalid state of a signal. In the embodiment of the present invention, not only the level state of a signal can characterize the valid or invalid state of a signal, but also the rising edge, falling edge or other features of a signal can be used to characterize the valid or invalid state of a signal.

[0036] Figure 4 FIG. 2 is a schematic diagram showing waveforms of various signals of the charging control circuit 23 according to an embodiment of the present invention. Figure 2 , Figure 3 and Figure 4 The working principle of the charging control circuit 23 will be described below.

[0037] exist Figure 4In the example, at time t1, the input voltage Vin drops to the charging window threshold Vr, and the charging window Cw1 begins. After the first duration T1, that is, at time t2, charging begins, and the input voltage control circuit 231 outputs the charging setting signal St to set the RS trigger FF1, so that it outputs the charging control signal Gc to control the charging current source Is to provide the charging current. The power supply capacitor Cvcc is charged, and the power supply voltage Vcc increases. After the charging duration Tc1, at time t3, the power supply voltage Vcc rises to the charging stop reference Vccd, and the power supply voltage comparison circuit 232 outputs the charging stop signal Rd to reset the RS trigger FF1, so that it outputs the charging control signal Gc to control the charging current source Is to stop providing the charging current. At the same time, the input voltage control circuit 231 starts timing when charging stops, and at time t4, the input voltage Vin rises to the charging window threshold, the charging window Cw1 ends, the timing ends, and the recorded duration is the second duration T2. After obtaining the duration data of the first duration T1 and the second duration T2, the preset duration Ts of the next charging window is updated to (T1+T2) / 2. That is, the charging cycle in the charging window Cw2 (t5-t8) starts at the moment after the preset duration Ts at time t5, that is, it starts at time t6. It should be understood that the preset duration Ts of the next charging window is the first duration T1 of the next charging window. According to the above working principle, the preset duration Ts in the charging window is adjusted in time. When the load of the power supply voltage Vcc does not change much, the charging cycle will be adjusted in time to both sides of the lowest point of the input voltage Vin and symmetrical along the lowest point of the input voltage Vin, thereby improving the charging efficiency of the input voltage Vin to the power supply voltage Vcc.

[0038] In some embodiments of the present invention, the preset duration Ts (i.e., the first duration T1 of the current charging window) is obtained by averaging the first duration T1 and the second duration T2 of the previous charging window. The second duration T2 starts from the moment charging stops and ends at the end of the charging window Cw1. Figure 2 In the circuit, the charging stop signal Rd is provided to the input voltage control circuit 231 to indicate the charging stop time. It should be understood by those skilled in the art that any signal that can be used to indicate charging stop, that is, the charging current source Is stops providing current, can be used to control the timing starting point of the second duration T2, such as the charging control signal Gc.

[0039] In some embodiments of the present invention, the preset duration Ts of the next charging window can also be obtained according to the charging window width and the charging cycle width of the current charging cycle. Figure 4 In the above example, Ts = (Tw-Tc1) / 2, where Tw is the duration of the charging window Cw1.

[0040] The first duration T1 and the second duration T2 may be characterized by specific timing durations. In some embodiments of the present invention, the first duration T1 and the second duration T2 may also be characterized by counting at a fixed frequency. For example, if the first duration T1 is characterized by counting 3 and the second duration T2 is characterized by counting 11, then the count of the preset duration Ts in the next charging window is 7. That is, after counting 7 at a fixed frequency from the starting point of the next charging window, the next charging cycle begins.

[0041] In some embodiments of the present invention, the charging cycle is within the charging window. When the charging window ends, the charging current source Is stops supplying power even if the charging cycle has not ended.

[0042] exist Figure 2 and Figure 4 In an embodiment, the power supply voltage comparison circuit 232 includes a comparator and a pulse circuit. The comparator compares the power supply voltage Vcc and the charge stop reference Vccd, and outputs a comparison signal representing the comparison result of the two. The pulse circuit receives the comparison signal and outputs a pulse signal based on the comparison signal. When the comparison signal represents that the power supply voltage Vcc rises to the charge stop reference Vccd, the pulse signal outputs a pulse. In some embodiments, the power supply voltage comparison circuit 232 includes a comparator. The comparator compares the power supply voltage Vcc and the charge stop reference Vccd, and outputs a comparison signal representing the comparison result of the two. The comparison signal is directly used as the charge stop signal Rd for resetting the RS trigger FF1.

[0043] In some applications, due to the influence of the subsequent circuit, for example, the coupling point between the voltage conversion control chip 21 and the input voltage Vin may have a high impedance, and the waveform of the input voltage Vin may not be as Figure 4 The complete steamed bun waveform shown in the figure may not be displayed as shown after filtering. Figure 4 In this case, the power supply voltage control circuit 22 cannot work normally, so the input voltage Vin needs to be processed so that it presents as follows Figure 4 The steamed bun waveform is shown.

[0044] Figure 5 FIG. 5 shows a schematic diagram of a circuit structure of a voltage conversion circuit 50 according to an embodiment of the present invention. Figure 5In the embodiment, the voltage conversion circuit 50 includes a power supply voltage control circuit 52. The power supply voltage control circuit 52 includes a power supply capacitor Cvcc, a charging current source Is, a charging control circuit 23, a leakage current source Il and a leakage control circuit 26. The leakage control circuit 26 receives the power supply voltage Vcc, and compares the power supply voltage Vcc with a leakage charging reference Lk1 and a leakage stop reference Lk2. When the power supply voltage Vcc is less than the leakage charging reference Lk1, the leakage control circuit 26 outputs a leakage control signal Lct to control the leakage current source Il to charge the power supply capacitor Cvcc. When the power supply voltage Vcc is greater than the leakage stop reference Lk2, the leakage control circuit 26 outputs a leakage control signal Lct to control the leakage current source Il to stop providing current. Figure 5 In the embodiment, the leakage control circuit 26 includes a leakage comparison circuit 261 and an RS trigger FF2. The leakage comparison circuit 261 compares the power supply voltage Vcc with the leakage charging reference Lk1 and the leakage stop reference Lk2, and provides a leakage set signal Ls and a leakage reset signal Lr according to the comparison result. The set terminal of the RS trigger FF2 receives the leakage set signal Ls, the reset terminal receives the leakage reset signal Lr, and the output terminal provides a leakage control signal Lct. In one embodiment, the leakage charging reference Lk1 is less than the leakage stop reference Lk2.

[0045] In some embodiments, the leakage comparison circuit 261 may be a hysteresis comparator. In other embodiments, the leakage comparison circuit 261 may also be two independent comparators.

[0046] exist Figure 5 In the embodiment, a small current is pulled down at the endpoint where the input voltage Vin is located through the leakage current source Il, thereby eliminating the influence of the internal high resistance and large parasitic capacitance of the voltage conversion control chip 21 on the input voltage Vin through the power supply voltage Vcc, so that the input voltage Vin maintains a steamed bun waveform, thereby allowing the power supply voltage control circuit 22 to operate normally.

[0047] In some embodiments, by properly setting the value of the charging window threshold Vr, for example, setting the value of the charging window threshold Vr at the input voltage Vin. Even if the input voltage Vin is The power supply voltage control circuit 22 can also work normally, so the leakage current source I1 and the leakage control circuit 26 are not needed.

[0048] Figure 6The circuit structure diagram of the voltage conversion circuit 60 according to an embodiment of the present invention is shown. The voltage conversion circuit 60 includes: a transformer T1, a primary switch M1, a secondary switch Ds, a power supply control chip 21, and a power supply voltage control circuit 22. The transformer T1 has a primary winding Lp, a secondary winding Ls, and an auxiliary winding Lt. The primary switch M1 is coupled to the primary winding Lp. The secondary switch Ds is coupled to the secondary winding Ls. The power supply control chip 21 outputs a primary control signal G1 to the control end of the primary switch M1 to control the on and off of the primary switch M1. The power supply control chip 21 is powered by a power supply voltage Vcc. The power supply voltage Vcc is formed by charging the power supply capacitor Cvcc by the charging current source Is. The power supply voltage control circuit 22 includes a charging control circuit 23, a current source Is, and a power supply capacitor Cvcc. The charging control circuit 23 receives the input voltage Vin and the power supply voltage Vcc, and outputs a charging control signal Gc to control the charging current source Is to charge the power supply capacitor Cvcc.

[0049] exist Figure 6 In the embodiment, the auxiliary winding Lt of the transformer T1 is coupled to the charging end of the power supply capacitor Cvcc through a diode Dt. When the voltage provided by the auxiliary winding Lt is higher than the voltage that can be reached by the charging control circuit 23 to control the charging current source Is to charge the power supply capacitor Cvcc, that is, the charging stop reference Vccd, the auxiliary winding Lt charges the power supply capacitor Cvcc. After understanding the principle of the present invention, those skilled in the art can set a reasonable value of the charging stop reference Vccd and the turns ratio between the auxiliary winding Lt and the secondary winding Ls according to application requirements, so that when the output voltage Vout is low, the charging control circuit 23 can be used to control the charging current source Is to charge the power supply capacitor Cvcc to maintain the power supply of the voltage conversion control chip 21, and when the output voltage Vout is high, the auxiliary winding Lt is used to charge the power supply capacitor Cvcc to maintain the power supply voltage Vcc.

[0050] When the output voltage Vout is low, the charging control circuit 23 is used to control the charging of the power supply capacitor Cvcc. It is not necessary to maintain a high turns ratio between the auxiliary winding Lt and the secondary winding Ls. The turns ratio between the two can be as low as 1:1, or even 1:2, or lower. When the turns ratio between the auxiliary winding Lt and the secondary winding Ls is 1:2, even if the output voltage Vout reaches 20V, the power supply voltage Vcc is only 10V. In other words, when the turns ratio between the auxiliary winding Lt and the secondary winding Ls is relatively low, even if the output voltage Vout is relatively high, the voltage provided by the auxiliary winding Lt will not be too high, causing the voltage conversion control chip 21 to need to withstand a higher voltage, and the circuit loss caused by the high voltage is also reduced.

[0051] Figure 7 FIG. 2 shows a schematic diagram of a circuit structure of a voltage conversion circuit 70 according to an embodiment of the present invention. Figure 6 Compared with the embodiment, Figure 7 In the embodiment, the voltage conversion circuit 70 includes a power supply voltage control circuit 52. As described above, when the power supply voltage Vcc is lower than the leakage charging reference Lk1, the leakage current source I1 charges the power supply capacitor Cvcc, and when the power supply voltage Vcc is higher than the leakage stop reference Lk2, the leakage current source I1 stops providing current.

[0052] It should be understood that the logic circuits in the embodiments of the present invention, such as the charging control logic circuit 233 and the trigger, are only used to illustrate the principles of the invention. When the polarity of the input and output signals of the logic circuit changes, the logic circuit will change accordingly.

[0053] In some embodiments, part or all of the charging control circuit 23, the leakage control circuit 26, the charging current source Is, and the leakage current source I1 are integrated into the voltage conversion control chip 21. In one embodiment, the charging current source Is includes a switch. The control end of the switch receives the charging control signal Gc.

[0054] It should be understood that the logic circuits in the embodiments of the present invention, such as the charging control logic circuit 233, the AND gate circuit and the trigger, are only used to illustrate the principles of the invention. When the polarity of the input and output signals of the logic circuit changes, the logic circuit will change accordingly.

[0055] The voltage conversion circuits 20, 50, 60 and 70 in the embodiment of the present invention have a Flyback topology. It should be understood that the power supply voltage control circuit in the embodiment of the present invention can be used for any voltage conversion circuit with other topologies, such as Buck topology, Boost topology, etc.

[0056] Figure 8 FIG. 8 is a flow chart of a power capacitor charging control method 80 according to an embodiment of the present invention. The power capacitor charging control method 80 can be used to control a charging current source to charge a power capacitor to establish a power supply voltage to supply power to a chip. The charging current source is coupled between an input voltage and a power capacitor. The chip can be Figure 2 , 5 -7 shows the voltage conversion control chip 21. The input voltage has a steamed wave, that is, a half-sine wave waveform after rectification of an AC voltage with a sinusoidal waveform. The power capacitor charging control method 80 includes: step 801, within the charging window, after a preset time has passed from the starting point of the charging window, controlling the charging current source to provide charging current to the power capacitor to generate a power supply voltage on the power supply capacitor; and step 802, when the power supply voltage is greater than the charging stop reference, controlling the charging current source to stop providing charging current; wherein, the charging window is symmetrically distributed on both sides of the lowest point of the input voltage with the lowest point of the input voltage as the midpoint.

[0057] In one embodiment, the power capacitor charging control method 80 also includes: step 803, adjusting the preset duration of the adjacent next charging window based on the first duration and the second duration of the current charging window; wherein the first duration of the current charging window corresponds to the preset duration in the current charging window, and the second duration of the current charging window corresponds to the duration from when the charging current source in the current charging window stops providing charging current to the end of the charging window.

[0058] In one embodiment, the power capacitor charging control method 80 further includes: step 804, adjusting the preset duration of the next adjacent charging window based on the charging window length in the current charging window and the duration of the charging current source providing the charging current.

[0059] In one embodiment, there is also a leakage current source between the input voltage and the power supply capacitor, and the power supply capacitor charging control method 80 also includes: step 805, when the power supply voltage is less than the leakage charging reference, controlling the leakage current source to provide leakage current to charge the power supply capacitor; and step 806, when the power supply voltage is greater than the leakage stop reference, controlling the leakage current source to stop providing leakage current.

[0060] There is no order requirement for the implementation of the steps of the power capacitor charging control method 80 .

[0061] In one embodiment, the drain stop reference is greater than the drain charge reference.

[0062] In one embodiment, the value of the leakage stop reference is the same as the value of the charge stop reference.

[0063] In one embodiment, the width of the charging window is adjusted based on a peak value of the input voltage.

[0064] In one embodiment, the charging window starts when the input voltage is less than a charging window threshold and ends when the input voltage rises to the charging window threshold.

[0065] In some embodiments, the charging window threshold is adjusted based on a peak value of the input voltage.

[0066] In some embodiments, the charging window threshold is a fixed value. In this case, when the frequency of the input voltage remains unchanged, the higher the peak value of the input voltage, the narrower the charging window, and the lower the peak value of the input voltage, the wider the charging window.

[0067] In some embodiments, the charging window threshold is proportional to the peak value of the input voltage. In this case, if the input voltage is a half-sine wave, the width of the charging window is related to the frequency of the input voltage, but has nothing to do with the magnitude of the input voltage. If the charging window threshold is 0.7×Vin_pk, the window width of the charging window is approximately Tin / 2, where Vin_pk is the peak value of the input voltage and Tin is the period of the input voltage with a half-sine wave.

[0068] In some embodiments, the value of the charging window threshold can be adjusted according to the peak value of the input voltage. For example, when the peak value of the input voltage Vin exceeds a threshold, the charging window threshold is a fixed value, and when the peak value of the input voltage is less than the threshold, the charging window threshold is proportional to the peak value of the input voltage, for example, the charging window threshold is 0.5×Vin_pk, where Vin_pk is the peak value of the input voltage.

[0069] It should be understood that the circuit and working process provided in the present invention are only for illustrative purposes, and any circuit that can implement the functions and working process of the circuit of the present invention does not deviate from the spirit or essence of the present invention.

[0070] Although the present invention has been described with reference to several typical embodiments, it should be understood that the terms used are illustrative and exemplary, rather than restrictive. Since the present invention can be embodied in a variety of forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims, so all changes and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A power supply voltage control circuit, comprising: A charging control circuit outputs a charging control signal based on an input voltage and a power supply voltage; as well as A charging current source, coupled to the input voltage, has a control terminal for receiving a charging control signal, and provides a charging current under the control of the charging control signal; Wherein, within the charging window, after a set time period has passed from the starting point of the charging window, the charging control signal controls the charging current source to provide charging current, and when the power supply voltage rises to the charging stop reference, the charging control signal controls the charging current source to stop providing charging current.

2. The power supply voltage control circuit according to claim 1, wherein: The charging window takes the lowest point of the input voltage as the midpoint and is symmetrically distributed on both sides of the lowest point of the input voltage.

3. The power supply voltage control circuit according to claim 1, wherein: The charging window starts when the input voltage drops to a charging window threshold and ends when the input voltage rises to the charging window threshold.

4. The power supply voltage control circuit as claimed in claim 3, wherein the charging window threshold is a fixed value.

5. The power supply voltage control circuit as claimed in claim 3, wherein the charging window threshold is proportional to a peak value of the input voltage.

6. The power supply voltage control circuit as claimed in claim 3, wherein when the peak value of the input voltage is greater than a threshold value, the charging window threshold value is a fixed value, and when the peak value of the input voltage is less than the threshold value, the charging window threshold value is proportional to the peak value of the input voltage.

7. The power supply voltage control circuit according to claim 1, wherein: The set duration is obtained based on the first duration and the second duration in the previous charging window, the first duration in the previous charging window being the duration from the starting point of the charging window in the previous charging window to the time when the charging current source provides the charging current, and the second duration in the previous charging window being the time when the charging current source stops providing the charging current in the previous charging window to the time when the charging window ends.

8. The power supply voltage control circuit according to claim 1, wherein: The set duration is obtained based on the length of the charging window in the previous charging window and the duration during which the charging current source provides the charging current.

9. The power supply voltage control circuit according to claim 1, wherein: The charging control circuit comprises: An input voltage control circuit provides a charging enable signal based on the input voltage; a power supply voltage comparison circuit, providing a charge stop signal based on the power supply voltage and a charge stop reference; and The charging control logic circuit outputs a charging control signal to control the charging current source based on the charging enable signal and the charging stop signal.

10. The power supply voltage control circuit as claimed in claim 1, further comprising: A leakage control circuit outputs a leakage control signal based on a power supply voltage, a leakage charge reference, and a leakage stop reference; as well as The leakage current source is connected in parallel with the charging current source and has a control terminal for receiving a leakage control signal and providing a leakage current under the control of the leakage control signal. Wherein, when the power supply voltage is less than the leakage charging reference, the leakage control signal controls the leakage current source to provide leakage current; When the power supply voltage is greater than the leakage stop reference, the leakage control signal controls the leakage current source to stop providing the leakage current.

11. The power supply voltage control circuit according to claim 10, wherein: The value of the leakage stop reference is the same as the value of the charge stop reference.

12. A power supply circuit, comprising the power supply voltage control circuit as claimed in any one of claims 1 to 11, and further comprising a power supply capacitor having a charging terminal coupled to a charging current source and a grounding terminal coupled to a reference ground.

13. The power supply circuit according to claim 12, wherein: The charging end of the power capacitor is also coupled to the auxiliary winding of the transformer of the voltage conversion circuit.

14. The power supply circuit according to claim 12, wherein: The charging current source includes a switch.

15. A voltage conversion circuit, comprising the power supply circuit according to claim 12, further comprising: A transformer having a primary winding and a secondary winding; A primary switch coupled to the primary winding; as well as The voltage conversion control chip outputs a primary control signal to the control end of the primary switch to control the on and off of the primary switch.

16. The voltage conversion circuit according to claim 15, wherein: The transformer further includes an auxiliary winding, and the auxiliary winding is coupled to the charging end of the power supply capacitor through a diode.

17. The voltage conversion circuit according to claim 15, wherein: The charging control circuit and the charging current source are integrated into a voltage conversion control chip.

18. A power supply capacitor charging control method, comprising: In the charging window, after a preset time period has passed from the starting point of the charging window, the charging current source is controlled to provide a charging current to the power capacitor, so as to generate a power voltage on the power capacitor; as well as When the power supply voltage is greater than the charging stop reference, the charging current source is controlled to stop providing the charging current; wherein the charging window takes the lowest point of the input voltage as the midpoint and is symmetrically distributed on both sides of the lowest point of the input voltage.

19. The power capacitor charging control method according to claim 18, further comprising adjusting a preset duration of an adjacent next charging window based on the first duration and the second duration of the current charging window.

20. The power capacitor charging control method of claim 18, further comprising adjusting a preset duration of an adjacent next charging window based on a charging window length of the current charging window and a duration for the charging power source to provide the charging current.

21. The power capacitor charging control method of claim 18, wherein the charging window starts when the input voltage drops to a charging window threshold and ends when the input voltage rises to the charging window threshold.

22. The power supply capacitor charging control method as claimed in claim 21, wherein the charging window threshold is a fixed value.

23. The power supply capacitor charging control method as claimed in claim 21, wherein the charging window threshold is proportional to the peak value of the input voltage.

24. The power capacitor charging control method as described in claim 21, wherein when the peak value of the input voltage is greater than a threshold, the charging window threshold is a fixed value, and when the peak value of the input voltage is less than the threshold, the charging window threshold is proportional to the peak value of the input voltage.

25. The power supply capacitor charging control method according to claim 18, further comprising: When the power supply voltage is less than the leakage charging reference, the leakage current source is controlled to provide leakage current; as well as When the power supply voltage is greater than the leakage stop reference, the leakage current source is controlled to stop providing the leakage current.

26. The power supply capacitor charging control method according to claim 25, wherein: The value of the leakage stop reference is greater than the value of the leakage charge reference.

27. The power supply capacitor charging control method according to claim 25, wherein: The value of the leakage stop reference is the same as the value of the charge stop reference.

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