CN115864790A - Frequency control system and method for switching power supply - Google Patents
Frequency control system and method for switching power supply Download PDFInfo
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Abstract
The invention discloses a frequency control system and a method of a switching power supply, wherein the system comprises: the voltage detection circuit is used for inputting a feedback voltage as an input signal and outputting a plurality of control signals for controlling the foldback circuit; the foldback circuit receives the control signal and generates a jump voltage or current signal; an oscillator circuit including a charging capacitor and generating a signal having a switching frequency based on a voltage of the charging capacitor; and the RC filter circuit is used for filtering the jumping voltage or current signal and generating a slowly-changed current signal, and the slowly-changed current signal is used as the charging current of the charging capacitor. According to the invention, through the RC filter circuit, the non-monotonous phenomena of output voltage overshoot, undershoot and the like at the frequency switching point of the output voltage of the switching power supply converter with the frequency foldback function in the soft start process can be effectively solved.
Description
Technical Field
The present invention relates to the field of switching power supply technologies, and in particular, to a frequency control system and method for a switching power supply.
Background
Switching power converters (DC/DC) use a frequency foldback function for better control of inductor current during soft start or under overload conditions. During soft start, or in the event of an overload, the output voltage VOUT of the DC/DC is significantly lower than the normal target value, causing the inductor current discharge slope to be slow. After such a plurality of switching cycles, the inductor current is liable to accumulate to a large value and even to run away. Therefore, the switching frequency Fsw needs to be reduced under these operating conditions, and a common method is a frequency foldback function.
The switching frequency is reduced to 1/8, 1/4 and 1/2 of the normal switching frequency, and the frequency foldback function is explained by taking the switching frequency as an example. When the switching power supply converter is in a normal working state, the target value VOUT0 of output voltage and the switching working frequency Fsw0 are output; in the soft start process, or when overload occurs, the output voltage VOUT is lower than the target value VOUT0, and the switching frequency Fsw is set according to the following conditions:
if VOUT < VOUT0 × 25%, fsw = Fsw0/8;
if VOUT0 × 25% < VOUT0 × 50%, fsw = Fsw0/4;
if VOUT0 x 50% < VOUT0 x 75%, fsw = Fsw0/2;
if VOUT0 x 75% < VOUT, fsw = Fsw0.
A common solution for implementing the frequency foldback function is shown in fig. 1. Generating an FB voltage from the VOUT voltage using a voltage dividing resistor, three comparators comparing the FB voltage with corresponding reference voltages 25, 50, and 75% c The comparator and RESET circuit RESET form an oscillating clock signal CLK, the operating waveform of which is shown in fig. 2.
The above technical solution can be expressed by a mathematical formula as:
in the scheme for realizing the frequency foldback function in the prior art, when the output voltage VOUT exceeds the threshold voltage set by the frequency foldback function, the switching frequency Fsw jumps once obviously, and the difference between the switching frequencies of two adjacent switching periods before and after frequency jump is obvious. The switching power converter adjusts the loop operating point to accommodate abrupt changes in the switching frequency. The adjustment process can cause overshoot and undershoot of the output voltage, so that the output voltage becomes non-monotonous and unsmooth. Fig. 3 illustrates a typical output voltage soft start waveform of a switching power converter with frequency foldback, and it can be seen that there is a significant overshoot of the output voltage at the switching frequency.
The frequency foldback function causes non-monotonic change such as overshoot and undershoot of the output voltage in the soft start process, which may cause malfunction of the subsequent stage load circuit, such as triggering the under-voltage locking function to operate repeatedly. Therefore, overshoot, undershoot and the like of the output voltage need to be avoided as much as possible.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
The invention aims to provide a frequency control system and a frequency control method of a switching power supply, which can solve the problems of overshoot and undershoot of output voltage caused by a frequency foldback function in the prior art, so that the output voltage VOUT can be smoothly and monotonically started in the soft start process.
To achieve the above object, an embodiment of the present invention provides a frequency control system of a switching power supply, including,
the voltage detection circuit is used for inputting a feedback voltage as an input signal and outputting a plurality of control signals for controlling the foldback circuit;
the foldback circuit receives the control signal and generates a jump voltage or current signal;
an oscillator circuit including a charging capacitor and generating a signal having a switching frequency based on a voltage of the charging capacitor;
and the RC filter circuit is used for filtering the jumping voltage or current signal and generating a slowly-changed current signal, and the slowly-changed current signal is used as the charging current of the charging capacitor.
In one or more embodiments of the present invention, the voltage detection circuit includes a plurality of first comparators comparing the feedback voltage with corresponding reference voltages to generate a plurality of control signals, respectively.
In one or more embodiments of the present invention, the foldback circuit includes a plurality of current branches, the plurality of current branches are connected in parallel and then connected to the RC filter circuit, at least one of the current branches is provided with a control switch, and a plurality of control signals output by the voltage detection circuit respectively control on or off of the control switch in the corresponding current branch.
In one or more embodiments of the present invention, the foldback circuit further includes a current source, and the current source generates a branch current on the current branch through a current mirror circuit, and a transistor connected in series with the control switch is disposed on the current branch.
In one or more embodiments of the present invention, the current signal filtered by the RC filter circuit passes through a current mirror circuit to generate the charging current of the charging capacitor.
In one or more embodiments of the invention, the foldback circuit includes a logic circuit that connects the RC filter circuit input to different reference voltages based on the control signal.
In one or more embodiments of the present invention, the output signal of the RC filter circuit generates a first current signal with a gradual change on a first resistor through a first buffer, and the first current signal generates the charging current of the charging capacitor through a current mirror circuit.
In one or more embodiments of the present invention, the foldback circuit includes a voltage dividing circuit, the voltage dividing circuit includes a plurality of resistors connected in series, at least one of the resistors is connected in parallel with a control switch, and a control signal output by the voltage detection circuit controls the corresponding control switch to be turned on or off to adjust an output voltage of the voltage dividing circuit; the output voltage of the voltage division circuit is used as the input of the RC filter circuit.
In one or more embodiments of the invention, the foldback circuit further includes a second buffer that generates a second current signal across a second resistor that is mirrored to the voltage divider circuit by a current mirror circuit.
In one or more embodiments of the invention, the output signal of the RC filter circuit generates a third current signal with a gradual change on a third resistor through a third buffer, and the third current signal generates the charging current of the charging capacitor through a current mirror circuit.
To achieve the above object, an embodiment of the present invention provides a frequency control method for a switching power supply, including:
the voltage detection circuit outputs a plurality of control signals for controlling the foldback circuit based on the input signal of the feedback voltage;
the foldback circuit receives the control signal and generates a jumping voltage or current signal;
the RC filter circuit filters the jumping voltage or current signal and generates a slowly changed current signal;
the slowly changed current signal is used as the charging current of a charging capacitor in the oscillator circuit;
the oscillator circuit generates a signal having a switching frequency based on the voltage of the charging capacitor.
Compared with the prior art, the invention can effectively solve the non-monotonous phenomena of output voltage overshoot, undershoot and the like at the frequency switching point of the output voltage of the switching power supply converter with the frequency foldback function in the soft start process through the RC filter circuit. Through smooth and gradual control of the charging current generating the switching frequency, switching of the switching frequency is also in smooth transition, and abnormal waveforms such as overshoot and undershoot on the output voltage VOUT are effectively avoided.
Drawings
FIG. 1 is a circuit schematic of a prior art switching power supply frequency control system;
FIG. 2 is a diagram illustrating waveforms of a comparator and a RESET circuit RESET for generating an oscillation clock signal CLK in the prior art;
FIG. 3 is a prior art soft start waveform of the output voltage of the switching power frequency control system;
fig. 4a is a circuit schematic diagram of a switching power supply frequency control system according to a first embodiment of the present invention;
fig. 4b is a soft start waveform of the output voltage of the frequency control system of the switching power supply according to the first embodiment of the invention;
fig. 5a is a circuit schematic of a switching power supply frequency control system according to a second embodiment of the present invention;
fig. 5b is a soft start waveform of the output voltage of the frequency control system of the switching power supply according to the second embodiment of the invention;
fig. 6a is a circuit schematic of a switching power supply frequency control system according to a third embodiment of the present invention;
fig. 6b is a soft start waveform of the output voltage of the frequency control system of the switching power supply according to the third embodiment of the present invention.
Detailed Description
Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the specific embodiments.
Throughout the specification and claims, unless explicitly stated otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or component but not the exclusion of any other element or component.
As shown in fig. 4a, the frequency control system 100 of the switching power supply according to the first embodiment of the present invention includes a voltage detection circuit 11, a foldback circuit 12, an oscillator circuit 13, and an RC filter circuit 14.
The voltage detection circuit 11 includes two series-connected voltage-dividing resistors 111 and 112, and 3 comparators 113, 114, 115. After the two voltage dividing resistors 111 and 112 are connected in series, one end is connected to the feedback voltage VOUT (system output voltage), and the other end is grounded. The positive phase inputs of the 3 comparators 113, 114, 115 are connected between the two voltage dividing resistors 111 and 122, and the negative phase inputs of the 3 comparators 113, 114, 115 are respectively connected with reference voltages V with different proportions REF 。
In one embodiment, the negative phase input of the comparator 113 is connected to 75% REF, outputting the control signal F3; the negative phase input of the comparator 114 is 50% ref, outputting the control signal F2; the negative phase input of the comparator 115 receives 25% of REF and outputs the control signal F1.
It should be noted that the number of the comparators 113 and the ratio of the negative phase input to the reference voltage can be adjusted according to the requirement, and the present disclosure is not limited thereto. For example, the number of comparators 113 may be 4, 5 or 6 as needed, and the comparator negative input may be 10% REF, 15% REF, 20% REF, 80% REF, or the like.
In this embodiment, the voltage detection circuit 11 generates the FB voltage from the feedback voltage VOUT through the voltage dividing resistors 111 and 112, and the FB voltage is used as the non-inverting input of the comparators 113, 114 and 115 to generate the logic control signals F3, F2 and F1 respectively, which are used to control the on/off of the switches.
The foldback circuit 12 receives the control signals F3, F2, F1 and generates a scaled current signal I k 。
In one embodiment, the foldback circuit 12 includes a current source 121 and four current branches. The four current branches are connected in parallel and then connected with the RC filter circuit 14.
Of the four current branches, a first current branch is provided with a transistor 123, a second current branch is provided with a transistor 124 and a control switch 127 which are connected in series, a third current branch is provided with a transistor 125 and a control switch 128 which are connected in series, and a fourth current branch is provided with a transistor 126 and a control switch 129 which are connected in series.
The current source 121 generates a current I B0 And branch currents of different proportions are formed on the four current branches by a current mirror circuit formed by the transistors 122. In one embodiment, 1/8I may be generated in the first current branch based on different aspect ratios of the transistors B0 1/8 of I can be generated on the second current branch B0 2/8 of I can be generated on the third current branch B0 4/8I can be generated on the fourth current branch B0 。
The control signals F1, F2, F3 are used to control the on/off of the control switches 127, 128, 129, respectively, so as to control the current signals I with different ratios k Is generated. For example, when all of the control switches 127, 128, 129 are on, I k ＝I B0 (ii) a When all the control switches 127, 128, 129 are open, I k I of =1/8 B0 (ii) a When the control switch 127 is turned on and the control switches 128 and 129 are turned off, I k I of =2/8 B0 (ii) a When the control switches 127 and 128 are turned on and the control switch 129 is turned off, I k I of =4/8 B0 。
In the technical scheme, the width-to-length ratio of the transistor in the current branch can be set as required, and the scheme is not limited. In addition, the number of the current branches provided with the control switches is correspondingly set according to the number of the control signals, for example, when the control signals include 4 groups, 4 current branches with the control switches are provided, and each group of control signals respectively controls the on-off of the control switches in 1 branch correspondingly.
The oscillator circuit 13 comprises a charging capacitor C OSC And based on a charging capacitor C OSC Voltage V of C A signal CLK with a switching frequency is generated.
In an embodiment, the oscillator circuit 13 further comprises a comparator 131 and a RESET circuit RESET, the comparator 131 and the RESET circuit RESET forming an oscillating clock signal CLK. In particular, the voltage V C As a positive input of the comparator 131, a negative input of the comparator 131 is connected to the reference voltage REF2. A RESET circuit RESET is provided between the non-inverting input and the output of the comparator 131, and includes a transistor 132 and a pulse generator 133.
In other embodiments, the pulse generator 133 may be eliminated from the RESET circuit RESET, and the pulse generator 133 may be connected to the output terminal of the comparator 131.
The RC filter circuit 14 is composed of a resistor R F And a capacitor C F Is configured to couple the transition current signal I k Filtering and generating a slowly varying current signal Ic as said charging capacitor C OSC The charging current of (2).
In one embodiment, the current signal filtered by the RC filter circuit 14 passes through the current mirror circuits 15 and 16 to generate the charging current Ic of the charging capacitor. The current mirror circuit 15 includes a transistor 151 and a transistor 152, and the current mirror circuit 16 includes a transistor 161 and a transistor 162.
The method for controlling the frequency control system 100 of the switching power supply according to the first embodiment of the present invention includes: VOUT voltage is detected by a set of comparators 113, 114, 115 to generate control signals F1, F2, F3, three of which control a current mirror to generate a scaled current I k . Current low pass filter 14 of RF/CF for I of jump k The current waveform is filtered and then the current mirror mirrors the charging current Ic of the capacitor Cosc of the oscillator 13.
Referring to FIG. 4b, each time the F1/F2/F3 switch toggles, I is caused k When the current jumps, the current low-pass filter 14 formed by the RF/CF will generate I k The current jump edge is smoothed to produce a slowly varying current Ic. The oscillation frequency generated by the oscillator 13 is also slowly varied. When the switching power converter responds to the slowly-changing switching frequency, the output voltage VOUT cannot generate voltage overshoot and undershoot, and the state that VOUT monotonically rises in the soft starting process is kept.
As shown in fig. 5a, the frequency control system 200 of the switching power supply according to the second embodiment of the present invention includes a voltage detection circuit, a foldback circuit 22, an oscillator circuit 23, and an RC filter circuit 24.
The voltage detection circuit employs the voltage detection circuit 11 in fig. 4a, and generates FB voltages from the feedback voltage VOUT through voltage dividing resistors 111, 112, which serve as non-inverting inputs of comparators 113, 114, 115 to generate logic control signals F3, F2, F1, respectively.
The foldback circuit 22 includes a logic circuit 221 and a 4-to-1 analog switch, and the 4-to-1 analog switch includes 4 selectable reference voltages of different ratios. The control signals F3, F2, F1 generate the control signals of the 1-out-of-4 analog switch through the logic circuit 221, and the input end of the RC filter circuit 24 can be connected to different reference voltages through different control signals.
In one embodiment, the voltages selectable by the 1-out-of-4 analog switch include REF2, REF2 of 1/4 and REF2 of 1/8. Correspondingly, the reference voltage is selected as follows:
selecting a REF2/8 reference voltage when F1= 0;
when F1=1&f2=0, REF2/4 voltage is selected;
selecting a REF2/2 voltage when F1=1&f2=1&f3= 0;
when F3=1, the REF2 voltage is selected.
It should be noted that when the number of the control signals is changed, for example, when the number is 4, more logic control combinations may be generated, the number of the reference voltages selectable by the analog switch may also be adaptively increased, and the ratio of the different reference voltages may be adjusted according to needs, which is not limited in this embodiment.
The oscillator circuit 23 comprises a charging capacitor C OSC And based on a charging capacitor C OSC Voltage V of C A signal CLK with a switching frequency is generated.
In an embodiment, the oscillator circuit 23 further comprises a comparator 231 and a RESET circuit RESET, the comparator 231 and the RESET circuit RESET forming an oscillating clock signal CLK. In particular, the voltage V C The positive input of the comparator 231 is connected to the negative input of the comparator 231 with the reference voltage REF3. A RESET circuit RESET is provided between the non-inverting input and the output of the comparator 231 to RESETThe circuit RESET comprises a transistor 232 and a pulse generator 233.
In other embodiments, the pulse generator 233 may be eliminated from the RESET circuit RESET, and the pulse generator 233 may be connected to the output terminal of the comparator 231.
The RC filter circuit 24 is composed of a resistor R F And a capacitor C F The circuit is used for filtering the accessed jump voltage signal and outputting a slowly-changed voltage signal REF2B.
The voltage signal REF2B generates a slowly varying current signal Iset across resistor Rset through buffer 25. Specifically, the voltage signal REF2B is connected to the positive input terminal of the buffer 25, a transistor 27 is connected between the negative input terminal and the output terminal of the buffer 25, and the transistor 27 is connected to the resistor Rset and then grounded.
The resistor Rset can be a resistor externally connected with the chip, and resistors with different resistance values can be selected as required to set the required switching frequency.
The current signal Iset passes through a current mirror circuit 26 to generate the charging capacitor C OSC The charging current Ic. The current mirror circuit 26 is constituted by a transistor 261 and a transistor 262.
In this embodiment, the 1-out-of-4 analog switch is followed by a voltage low pass filter 24 formed by RC, so that the reference voltage REF2B has a gradual process based on REF2, as shown in fig. 5B. REF2B generates a current Iset across resistor Rset through buffer 25, also with a slowly changing transition edge, and finally mirrors the charging current Ic to oscillator capacitor Cosc. Therefore, the oscillation frequency generated by the oscillator is also changed slowly, and voltage overshoot and undershoot generated by the VOUT voltage can be avoided.
As shown in fig. 6a, the frequency control system 300 of the switching power supply according to the third embodiment of the present invention includes a voltage detection circuit, a foldback circuit 32, an oscillator circuit 33, and an RC filter circuit 34.
The voltage detection circuit employs the voltage detection circuit 11 in fig. 4a, and generates FB voltage from the feedback voltage VOUT through voltage-dividing resistors 111, 112, which is used as non-inverting input of comparators 113, 114, 115 to generate logic control signals F3, F2, F1, respectively.
One end of the 4 resistors connected in series is grounded, and the other end is connected to the RC filter circuit 34.
It should be noted that when the number of the control signals is changed, for example, when the number of the control signals is 4 groups, more logic control combinations may be generated, at this time, the number of the resistors may also be adaptively increased to 5, and the resistance ratio of the different resistors may be adjusted according to needs, which is not limited in this embodiment.
The voltage signal REF2 generates a current signal Iset that transitions across the resistor Rset through the buffer 322. The current signal Iset further generates a mirrored current at the voltage divider circuit through the current mirror circuit 323.
Specifically, the voltage signal REF2 is connected to the positive input terminal of the buffer 322, a transistor 323 is connected between the negative input terminal and the output terminal of the buffer 322, and the transistor 323 is connected to the resistor Rset and then grounded. The current mirror circuit 323 is constituted by a transistor 3231 and a transistor 3232.
The oscillator circuit 33 comprises a charging capacitor C OSC And based on a charging capacitor C OSC Voltage V of C A signal CLK with a switching frequency is generated.
In an embodiment, the oscillator circuit 33 further comprises a comparator 331 and a RESET circuit RESET, the comparator 331 and the RESET circuit RESET forming an oscillating clock signal CLK. In particular, the voltage V C The positive input of the comparator 331 is connected to the reference voltage REF3, and the negative input of the comparator 331 is connected to the positive input of the comparator 331. A RESET circuit RESET is provided between the non-inverting input and the output of the comparator 331, and includes a transistor 332 and a pulse generator 333.
The RC filter circuit 34 is composed of a resistor R F And a capacitor C F The filter is used for filtering the connected jump voltage signal and outputting a slowly-changed voltage signal REF2B.
Voltage signal REF2B is passed through buffer 35 at resistor R 2 Generating a slowly varying current signal I 2 . Specifically, the voltage signal REF2B is connected to the positive input terminal of the buffer 35, and a transistor 37 is connected between the negative input terminal and the output terminal of the buffer 35, the transistor 37 and the resistor R 2 And after connection, the grounding is connected.
Resistance R 2 The resistor can be externally connected with the chip, and resistors with different resistance values can be selected according to requirements to set the required switching frequency.
Current signal I 2 The charging capacitance C is generated by a current mirror circuit 36 OSC The charging current Ic. The current mirror circuit 36 is constituted by a transistor 361 and a transistor 362.
In this embodiment, the control method of the frequency control system 300 of the switching power supply includes: the REF2 voltage recovers to a voltage at the resistor Rset through the current Iset generated by the buffer 322 at the resistor Rset at the resistor string R1/8, R1/4, the voltage is controlled by three signals F1, F2 and F3, and a jump voltage is generated when F1/F2/F3 changes; the RF/CF form of the voltage low pass filter 34 filters the transition voltage to produce a gently changing voltage REF2B, as shown in FIG. 6B. The REF2B voltage is then converted into a current through the buffer 35 on the resistor R2, and finally mirrored to obtain the charging current Ic of the oscillator capacitor Cosc. Therefore, the oscillation frequency generated by the oscillator is also changed slowly, and voltage overshoot and undershoot generated by the VOUT voltage can be avoided. Compared with the second technical implementation scheme, the scheme is more suitable for the situation that Rset is the switching frequency set by the chip external resistor, and the problem that the voltage on the Rset is too low and is easily interfered can be avoided.
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.
Claims (11)
1. A frequency control system for a switching power supply, comprising:
the voltage detection circuit has an input signal of a feedback voltage and an output signal of a plurality of control signals for controlling the foldback circuit;
the foldback circuit receives the control signal and generates a jump voltage or current signal;
an oscillator circuit including a charging capacitor and generating a signal having a switching frequency based on a voltage of the charging capacitor;
and the RC filter circuit is used for filtering the jumping voltage or current signal and generating a slowly-changed current signal, and the slowly-changed current signal is used as the charging current of the charging capacitor.
2. The frequency control system of the switching power supply according to claim 1, wherein the voltage detection circuit comprises a plurality of first comparators, and the plurality of first comparators respectively compare the feedback voltage with corresponding reference voltages to generate the plurality of control signals.
3. The frequency control system of the switching power supply according to claim 2, wherein the foldback circuit comprises a plurality of current branches, the plurality of current branches are connected to the RC filter circuit in parallel, at least one of the current branches is provided with a control switch, and the plurality of control signals output by the voltage detection circuit respectively control the on/off of the control switch in the corresponding current branch.
4. The frequency control system of a switching power supply according to claim 3, wherein said foldback circuit further comprises a current source for generating a branch current in said current branch via a current mirror circuit,
and a transistor connected with the control switch in series is arranged on the current branch circuit.
5. The frequency control system of the switching power supply according to claim 3, wherein the current signal filtered by the RC filter circuit passes through a current mirror circuit to generate the charging current of the charging capacitor.
6. The frequency control system of a switching power supply according to claim 2, wherein the foldback circuit includes a logic circuit to connect the RC filter circuit input to different reference voltages based on the control signal.
7. The frequency control system of a switching power supply according to claim 6, wherein the output signal of said RC filter circuit generates a first current signal varying gradually at a first resistor through a first buffer,
the first current signal passes through a current mirror circuit to generate a charging current of the charging capacitor.
8. The frequency control system of the switching power supply according to claim 2, wherein the foldback circuit comprises a voltage dividing circuit, the voltage dividing circuit comprises a plurality of resistors connected in series, at least one of the resistors is connected in parallel with a control switch, and the control signal output by the voltage detection circuit controls the corresponding control switch to be turned on or off so as to adjust the output voltage of the voltage dividing circuit;
and the output voltage of the voltage division circuit is used as the input of the RC filter circuit.
9. The frequency control system of a switching power supply of claim 8, wherein the foldback circuit further comprises a second buffer, the second buffer generating a second current signal across a second resistor,
the second current signal is mirrored to the voltage divider circuit by a current mirror circuit.
10. The frequency control system of a switching power supply according to claim 8 or 9, wherein the output signal of said RC filter circuit generates a third current signal varying slowly across a third resistor through a third buffer,
the third current signal generates a charging current of the charging capacitor through a current mirror circuit.
11. A method for controlling frequency of a switching power supply, comprising:
the voltage detection circuit outputs a plurality of control signals for controlling the foldback circuit based on the input signal of the feedback voltage;
the foldback circuit receives the control signal and generates a hopping voltage or current signal;
the RC filter circuit filters the jumping voltage or current signals and generates slowly changing current signals;
the slowly changed current signal is used as the charging current of a charging capacitor in the oscillator circuit;
the oscillator circuit generates a signal having a switching frequency based on the voltage of the charging capacitor.
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| CN117155094A (en) * | 2023-07-20 | 2023-12-01 | 北京伽略电子股份有限公司 | Overcurrent protection circuit and DC-DC converter |
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| CN117155094A (en) * | 2023-07-20 | 2023-12-01 | 北京伽略电子股份有限公司 | Overcurrent protection circuit and DC-DC converter |
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