CN211701851U - Switch power supply - Google Patents

Switch power supply Download PDF

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Publication number
CN211701851U
CN211701851U CN202020218466.XU CN202020218466U CN211701851U CN 211701851 U CN211701851 U CN 211701851U CN 202020218466 U CN202020218466 U CN 202020218466U CN 211701851 U CN211701851 U CN 211701851U
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resistor
electrically connected
circuit
transistor
diode
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万鹏
万辉
赖洋林
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Kuaibei New Energy Technology Shanghai Co ltd
Shanghai Tn Industrial Co ltd
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Kuaibei New Energy Technology Shanghai Co ltd
Shanghai Tn Industrial Co ltd
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Abstract

The embodiment of the utility model discloses switching power supply, include: MOS pipe still includes: the input end of the power-on starting circuit and the first pole of the MOS tube are both connected with a power supply signal; the input end of the signal generating circuit is electrically connected with the output end of the power-on starting circuit, and the signal generating circuit is used for generating a PWM signal according to the power-on starting signal; the MOS tube control circuit comprises an input end of the MOS tube control circuit, an output end of the power-on starting circuit is electrically connected with the output end of the power-on starting circuit, a control end of the MOS tube control circuit is electrically connected with an output end of the signal generating circuit, and an output end of the MOS tube control circuit is electrically connected with a grid electrode of the MOS tube. The embodiment of the utility model provides a switching power supply can realize adjusting switching power supply's output voltage's purpose, and then makes output voltage electric current's scope great, satisfies the circuit that has different supply voltage demands.

Description

Switch power supply
Technical Field
The embodiment of the utility model provides a relate to switching power supply technique, especially relate to a switching power supply.
Background
The power supply is an energy source of all electric equipment, and the electric equipment needs the power supply to supply required working voltage for normal work. With the development and innovation of power electronic technology, the technology of the switching power supply is continuously innovated. At present, the switching power supply is widely applied to electronic equipment due to the characteristics of small size, light weight and high efficiency, and is an indispensable power supply mode for the rapid development of the electronic information industry at present.
At present, most of the existing switching power supplies are realized by using a power supply control IC, although the cost of the power supply control IC is low, the control frequency of the power supply control IC is constant or can only change within a small range, the power supply control IC is a semiconductor device, partial functions can only be completed by assistance of an additional circuit, and the applicable voltage and current range is small due to the difference of each power supply control IC.
SUMMERY OF THE UTILITY MODEL
An embodiment of the utility model provides a switching power supply to realize adjusting switching power supply's output voltage's purpose, and then make output voltage electric current's scope great, satisfy the circuit that has different supply voltage demands.
In a first aspect, an embodiment of the present invention provides a switching power supply, including: MOS pipe still includes:
the power-on starting circuit is used for outputting a power-on starting signal according to the power signal;
the input end of the signal generating circuit is electrically connected with the output end of the power-on starting circuit, and the signal generating circuit is used for generating a PWM signal according to the power-on starting signal;
the MOS pipe control circuit, the input of MOS pipe control circuit is connected with last electric starting circuit's output electricity, and the control end of MOS pipe control circuit is connected with signal generation circuit's output electricity, and the output of MOS pipe control circuit is connected with the grid electricity of MOS pipe, and MOS pipe control circuit is used for generating MOS pipe control signal according to the PWM signal, controls the break-make of MOS pipe, and the MOS pipe switches on, output voltage signal.
Optionally, the power-on starting circuit includes a first triode, a second triode, a first diode, a first capacitor, a first resistor, a second resistor and a third resistor, a first end of the first resistor is used as an input end of the power-on starting circuit, a second end of the first resistor is grounded through the first capacitor, a first pole of the first triode is electrically connected with a second end of the first resistor, a base of the first triode is electrically connected with a cathode of the first diode through the second resistor, an anode of the first diode is grounded, a first pole of the second triode is electrically connected with an anode of the first diode, a second pole of the second triode is grounded, a base of the second triode is electrically connected with a second pole of the first triode through the third resistor, and a second pole of the first triode is used as an output end of the power-on starting circuit.
Optionally, the signal generating circuit includes a triangular wave circuit and a PWM wave circuit, an input end of the triangular wave circuit and an input end of the PWM wave circuit are both used as input ends of the signal generating circuit, an output end of the triangular wave circuit is electrically connected with a control end of the PWM wave circuit, an output end of the PWM wave circuit is used as an output end of the signal generating circuit, the triangular wave circuit is used for generating a triangular wave with adjustable frequency, and the PWM wave circuit is used for generating a PWM wave with corresponding frequency according to the triangular wave.
Optionally, the triangular wave circuit includes a second capacitor, a third capacitor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, and a first comparator, a first end of the fourth resistor and a first end of the second capacitor are used as input ends of the triangular wave circuit, a second end of the second capacitor is grounded, a second end of the fourth resistor is electrically connected to a positive input end of the first comparator, an output end of the first comparator is electrically connected to a first end of the fifth resistor, a negative input end of the first comparator is electrically connected to a second end of the fifth resistor, a second end of the fifth resistor is grounded through the third capacitor, a first end of the sixth resistor is electrically connected to a first end of the fourth resistor, a second end of the sixth resistor is electrically connected to a first end of the seventh resistor, a second end of the seventh resistor and a first end of the eighth resistor are both electrically connected to a second end of the fourth resistor, a second end of the eighth resistor is grounded, and the second end of the fifth resistor is used as the output end of the triangular wave circuit.
Optionally, the PWM wave circuit includes an adjustable resistor, a second comparator, a third transistor, a fourth capacitor, a ninth resistor, a tenth resistor, an eleventh resistor, and a twelfth resistor, a reverse input end of the second comparator is used as a control end of the PWM wave circuit, a forward input end of the second comparator is electrically connected to a first electrode of the third transistor, a second electrode of the third transistor is grounded, a base of the third transistor is electrically connected to a first end of the adjustable resistor, a second end of the adjustable resistor is used as an input end of the PWM wave circuit, a second end of the adjustable resistor is electrically connected to an adjustable end of the adjustable resistor, a first end of the ninth resistor is electrically connected to a base of the third transistor, a second end of the ninth resistor is grounded, a first end of the tenth resistor and a first end of the eleventh resistor are both electrically connected to a second end of the adjustable resistor, a second end of the tenth resistor is electrically connected to a forward input end of the second comparator, the second end of the eleventh resistor is electrically connected with the output end of the second comparator, the first end of the twelfth resistor is electrically connected with the second end of the eleventh resistor, the second end of the twelfth resistor is grounded, the first end of the fourth capacitor is electrically connected with the positive input end of the second comparator, the second end of the fourth capacitor is grounded, and the output end of the second comparator is used as the output end of the PWM wave circuit.
Optionally, the switching power supply further includes a second diode, the second diode and the power-on start circuit form a bootstrap circuit, an anode of the second diode is electrically connected to a second pole of the MOS transistor, and a cathode of the second diode is electrically connected to the first pole of the first triode.
Optionally, the switching power supply further includes a voltage loop circuit, the voltage loop circuit includes a fourth triode, a third diode and a thirteenth resistor, a cathode of the third diode is electrically connected to a cathode of the second diode as an input terminal of the voltage loop circuit, an anode of the third diode is electrically connected to a base of the fourth triode through the thirteenth resistor, a first pole of the fourth triode is grounded, and a second pole of the fourth triode is electrically connected to a second end of the adjustable resistor as an output terminal of the voltage loop circuit.
Optionally, the switching power supply further includes a voltage-reducing circuit, the voltage-reducing circuit includes an inductor, a fourth diode, a light-emitting diode, a fifth capacitor, a sixth capacitor, a fourteenth resistor and a fifteenth resistor, an anode of the second diode is electrically connected with a second electrode of the MOS transistor through the inductor, a second end of the inductor is electrically connected with the second electrode of the MOS transistor as an input end of the voltage-reducing circuit, a first end of the inductor is electrically connected with an anode of the second diode as an output end of the voltage-reducing circuit, a first end of the inductor is grounded through the fifth capacitor, the sixth capacitor and the fourteenth resistor, a first end of the inductor is electrically connected with an anode of the light-emitting diode through the fifteenth resistor, a cathode of the light-emitting diode is grounded, a second end of the inductor is electrically connected with a cathode of the fourth diode, and an.
Optionally, the MOS pipe control circuit includes the fifth triode, the sixth triode, sixteenth resistance and seventeenth resistance, the input of MOS pipe control circuit is regarded as to the first utmost point of fifth triode, the control end of MOS pipe control circuit is all regarded as to the base of fifth triode and the base of sixth triode, the second pole of fifth triode and the first electric connection of sixth triode, the second pole ground connection of sixth triode, the first end of sixteenth resistance is connected with the second pole electricity of fifth triode, the second end of sixteenth resistance is through seventeenth resistance ground connection, the second end of sixteenth resistance is as the output of MOS pipe control circuit.
Optionally, the switching power supply further includes a current loop circuit, the current loop circuit includes a seventh triode, a seventh capacitor, an eighteenth resistor and a nineteenth resistor, the first end of the eighteenth resistor and the first end of the nineteenth resistor are both electrically connected to the second pole of the MOS transistor as the input end of the current loop circuit, the second end of the eighteenth resistor is grounded, the second end of the nineteenth resistor is electrically connected to the base of the seventh triode, the base of the seventh triode is grounded through the fifth capacitor, the first pole of the seventh triode is grounded, and the second pole of the seventh triode is electrically connected to the output end of the signal generating circuit as the output end of the current loop circuit.
The embodiment of the utility model provides a switching power supply, including the MOS pipe, go up electric starting circuit, signal generation circuit and MOS pipe control circuit, go up electric starting circuit's input and the first utmost point of MOS pipe and all insert power signal, go up electric starting circuit and go up electric starting signal according to power signal output, signal generation circuit generates the PWM signal according to last electric starting signal, MOS pipe control circuit generates MOS pipe control signal according to the PWM signal, the break-make of control MOS pipe, the MOS pipe switches on, output voltage signal. The embodiment of the utility model provides a switching power supply, accessible signal generation circuit control PWM signal's duty cycle to the duty cycle of control MOS pipe control signal, thereby the duty cycle of adjustment MOS pipe output voltage signal realizes adjusting switching power supply's output voltage's purpose, and then makes output voltage electric current's scope great, satisfies the circuit that has different supply voltage demands.
Drawings
Fig. 1 is a schematic structural diagram of a switching power supply according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a triangular wave and a rectangular wave according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
Fig. 1 is a schematic structural diagram of a switching power supply provided by the embodiment of the present invention, this embodiment is applicable in the equipment that needs the switching power supply to supply power, refer to fig. 1, this switching power supply includes: a MOS transistor Q8, a power-on start circuit 100, a signal generation circuit 110, and a MOS transistor control circuit 120.
The input end of the power-on starting circuit 100 and the first electrode of the MOS transistor Q8 are both connected to a power signal Vin, and the power-on starting circuit 100 is configured to output a power-on starting signal VCC according to the power signal Vin; the input end of the signal generating circuit 110 is electrically connected to the output end of the power-on starting circuit 100, and the signal generating circuit 110 is configured to generate a PWM signal according to the power-on starting signal; the input end of the MOS tube control circuit 120 is electrically connected to the output end of the power-on start-up circuit 100, the control end of the MOS tube control circuit 120 is electrically connected to the output end of the signal generation circuit 110, the output end of the MOS tube control circuit 120 is electrically connected to the gate of the MOS tube Q8, the MOS tube control circuit 120 is configured to generate a MOS tube control signal according to the PWM signal, control the on/off of the MOS tube Q8, and the MOS tube Q8 is turned on to output a voltage signal.
Specifically, the voltage of the power signal Vin, which is connected to both the input end of the power-on starting circuit 100 and the first pole of the MOS transistor Q8, may be obtained by performing full-wave shaping and capacitive filtering after the ac voltage is reduced by the transformer, and the voltage of the power signal Vin is 31V, for example, the power-on starting circuit 100 outputs the power-on starting signal VCC according to the power signal Vin, so as to supply power to the signal generating circuit 110 and the MOS transistor control circuit 120, the signal generating circuit 110 may generate a PWM signal and may adjust the duty ratio of the PWM signal, the signal generating circuit 110 outputs the PWM signal to the MOS transistor control circuit 120, the MOS transistor control circuit 120 may generate a MOS transistor control signal according to the PWM signal, the duty ratio of the MOS transistor control signal is adjusted by the signal generating circuit 110, and the MOS transistor Q8 is controlled by the MOS transistor control signal, the power supply signal Vin provides an input voltage for the MOS transistor Q8, and the MOS transistor Q8 outputs the voltage signal Vout from the second pole when being turned on, so as to control the on-off time of the MOS transistor Q8 by controlling the duty ratio of the MOS transistor control signal, so as to adjust the voltage of the output voltage signal Vout, thereby providing the voltage required by normal operation for the device requiring power supply. And the voltage of the output voltage signal Vout is less than that of the power signal Vin, for example, when the voltage of the power signal Vin is 31V, the voltage of the output voltage signal Vout is 12V, and the maximum output current Iout is 1A.
The switching power supply provided by the embodiment can control the duty ratio of the PWM signal by changing the signal generating circuit so as to control the duty ratio of the MOS tube control signal, thereby adjusting the duty ratio of the output voltage signal of the MOS tube, realizing the purpose of adjusting the output voltage of the switching power supply, further enabling the range of the output voltage current to be larger, and meeting the circuit with different power supply voltage requirements.
Optionally, the power-on start circuit 100 includes a first transistor Q1, a second transistor Q2, a first diode D1, a first capacitor C1, a first resistor R1, a second resistor R2, and a third resistor R3, wherein a first end of the first resistor R1 serves as an input end of the power-up starting circuit 100, a second end of the first resistor R1 is grounded through the first capacitor C1, a first pole of the first transistor Q1 is electrically connected to a second end of the first resistor R1, a base of the first transistor Q1 is electrically connected to a cathode of the first diode D1 through the second resistor R2, an anode of the first diode D1 is grounded, a first pole of the second transistor Q2 is electrically connected to an anode of the first diode D1, a second pole of the second transistor Q2 is grounded, a base of the second transistor Q2 is electrically connected to a second pole of the first transistor Q1 through the third resistor R3, and a second pole of the first transistor Q1 serves as an output end of the power-up starting circuit 100.
Wherein the first diode D1 is a voltage regulator diode, the power-on start circuit 100 charges the first capacitor C1 with the voltage of the power signal Vin through the first resistor R1, if the voltage of the first diode D1 is 10V, when the charging voltage of the first capacitor C1 reaches 10.7V, Vcb of the first transistor Q1 is 0.7V, if the first transistor Q1 is a PNP type transistor, then the first transistor Q1 is conducted, since the Vce of the first transistor Q1 is 0.3V when it is turned on, the voltage of the power-on enable signal VCC is 10.4V, if the second transistor Q2 is an NPN transistor, the power-up enable signal VCC turns on the second transistor Q2 through the resistor R10 at this time, namely, the second resistor R2, the first diode D1 and the NPN transistor Q4 are grounded at the electrical connection point of the second transistor Q2, at this time, the first transistor Q1 is fully saturated and turned on, the power-on start is completed, and the voltage of the power-on start signal VCC is 10.4V.
It should be noted that the regulated value of the voltage across the first diode D1 is only a schematic illustration, and is determined according to practical situations, and is not limited herein, and the first transistor Q1 may also be an NPN type, and the second transistor Q2 may also be a PNP type, and is not limited specifically.
Optionally, the signal generating circuit 110 includes a triangular wave circuit 111 and a PWM wave circuit 112, an input end of the triangular wave circuit 111 and an input end of the PWM wave circuit 112 are both used as input ends of the signal generating circuit 110, an output end of the triangular wave circuit 111 is electrically connected to a control end of the PWM wave circuit 112, an output end of the PWM wave circuit 112 is used as an output end of the signal generating circuit 110, the triangular wave circuit 111 is configured to generate a triangular wave with adjustable frequency, and the PWM wave circuit 112 is configured to generate a PWM wave with corresponding frequency according to the triangular wave.
The triangular wave circuit 111 outputs triangular waves with adjustable frequency, the PWM wave circuit 112 generates rectangular waves according to the triangular waves output by the triangular wave circuit 111, the frequency of the rectangular waves is the same as that of the triangular waves, the frequency of the rectangular waves can be adjusted by adjusting the frequency of the triangular waves, and the PWM wave circuit 112 can control the duty ratio of the output rectangular waves, so as to provide control signals of the rectangular waves with adjustable duty ratio for the MOS tube control circuit 120.
Optionally, the triangular wave circuit 111 includes a second capacitor C2, a third capacitor C3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, and a first comparator U1A, a first end of the fourth resistor R4 and a first end of the second capacitor C2 are used as input ends of the triangular wave circuit 111, a second end of the second capacitor C2 is grounded, a second end of the fourth resistor R4 is electrically connected to a forward input end of the first comparator U1A, an output end of the first comparator U1A is electrically connected to a first end of the fifth resistor R2, an inverting input end of the first comparator U1A is electrically connected to a second end of the fifth resistor R5, a second end of the fifth resistor R5 is grounded via the third capacitor C3, a first end of the sixth resistor R6 is electrically connected to a first end of the fourth resistor R4, a second end of the sixth resistor R6 is electrically connected to a second end of the seventh resistor R6, and a second end of the eighth resistor R6, the second terminal of the eighth resistor R8 is grounded, and the second terminal of the fifth resistor R5 serves as the output terminal of the triangular wave circuit 111.
Specifically, according to the circuit structure of the triangular wave circuit 111 in fig. 1, the voltage of the pin 3 of the first comparator U1A is VCC R8/[ R4| (R7+ R6) + R8], and the voltage of the pin 3 of the first comparator U1A can be obtained according to the voltage magnitude of VCC and the resistance values of the resistors, if VCC is 10.4V and the resistance values of the resistors in the above formula are all 10K, the voltage of the pin 3 of the first comparator U1A is 6.24V, the voltage of the pin 2 of the first comparator U1A is 0V, and at this time, the pin 1 of the first comparator U1A outputs a high level of 10.4V, and the third capacitor C3 is charged; when the charging voltage across the third capacitor C3 reaches 6.24V or more, the voltage of pin 2 of the third capacitor C3 is higher than the voltage of pin 3, at this time, pin 1 of the third capacitor C3 will output a low level of 0V, the third capacitor C3 will discharge the 0V of pin 1 of the first comparator U1A through the fifth resistor R5, and the voltage of pin 3 of the first comparator U1A is VCC (R2| | R3)/(R1+ R2| | | R3) ═ 10.4 ═ 5K/(10K +5K) × 3.5V; when the discharging voltage at two ends of the third capacitor C3 reaches below 3.5V, the voltage of pin 2 of the first comparator U1A is lower than that of pin 3, pin 1 outputs high level of 10.4V, the third capacitor C3 charges the voltage of pin 1 of the first comparator U1A through the fifth resistor R5, when the charging voltage at two ends of the third capacitor C3 reaches above 6.24V, the discharging charging is repeated, at this time, the third capacitor C3, the fifth resistor R5 and the 2-pin electric connection node of the first comparator U1A form a triangular wave output, the frequency of the triangular wave is determined by the size of the third capacitor C3 and the fifth resistor R5, when the value of the capacitor C1 is 3.3nF and the value of the resistor R5 is 10K, the frequency of the output triangular wave is about 68KHz, in practical application, the values of the capacitors C1 and the resistor R5 can be changed, and the frequency of the output triangular wave can be detected by detecting the frequency of the output triangular oscilloscope.
Optionally, the PWM wave circuit 112 includes an adjustable resistor R20, a second comparator U1B, a third transistor Q3, a fourth capacitor C4, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11 and a twelfth resistor R12, the inverting input terminal of the second comparator U1B serves as the control terminal of the PWM wave circuit 112, the forward input terminal of the second comparator U1B is electrically connected to the first terminal of the third transistor Q3, the second terminal of the third transistor Q3 is grounded, the base of the third transistor Q3 is electrically connected to the first terminal of the adjustable resistor R20, the second terminal of the adjustable resistor R20 serves as the input terminal of the PWM wave circuit 112, the second terminal of the adjustable resistor R20 is electrically connected to the adjustable terminal of the adjustable resistor R20, the first terminal of the ninth resistor R9 is electrically connected to the base of the third transistor Q3, the second terminal of the ninth resistor R9 is grounded, the first terminal of the tenth resistor R10 and the eleventh terminal of the adjustable resistor R11 are electrically connected to the second terminal of the adjustable resistor R20, a second end of the tenth resistor R10 is electrically connected to the positive input terminal of the second comparator U1B, a second end of the eleventh resistor R11 is electrically connected to the output terminal of the second comparator U1B, a first end of the twelfth resistor R12 is electrically connected to a second end of the eleventh resistor R11, a second end of the twelfth resistor R12 is grounded, a first end of the fourth capacitor C4 is electrically connected to the positive input terminal of the second comparator U1B, a second end of the fourth capacitor C4 is grounded, and an output terminal of the second comparator U1B serves as an output terminal of the PWM wave circuit 112.
Specifically, fig. 2 is a schematic diagram of a triangular wave and a rectangular wave according to an embodiment of the present invention, in combination with fig. 1 and fig. 2, the power-on start signal VCC charges a fourth capacitor C4 through a tenth resistor R10, when the charging voltage of a fourth capacitor C4 is higher than the voltages of an adjustable resistor R20 and a ninth resistor R9, the fourth capacitor C4 divides the voltage of the power-on start signal VCC so that the Vcb of a third transistor Q3 is 0.7V, if the third transistor Q3 is a PNP type transistor, the power-on start signal VCC no longer charges the fourth capacitor C4, the voltage of a fourth capacitor C4 is VCC R9/(R9+ R20) +0.7V, the adjustable resistor R15 is adjusted to have a resistance value of 13.6K according to the above formula, if the stable voltage of the fourth capacitor C4 is 5.1V, when the resistance of the tenth resistor R10 is 10K, the power-on start signal VCC is completed from the start circuit 100V, the time required for the voltage of the fourth capacitor C4 to charge from 0V to 5.1V is approximately 20 milliseconds, and the fourth capacitor C4 is electrically connected to the pin 5 of the second comparator U1B, so that the output waveform at pin 7 of the second comparator U1B can be represented by a square wave in fig. 2, as can be seen from the waveform diagram of fig. 2, during many periods when the triangular wave is generated initially, the amplitude of the triangular wave is always higher than the voltage amplitude of the 5 pin of the second comparator U1B, the level of the 7 pin of the second comparator U1B is always zero during this period, when the amplitude of the triangular wave crosses the voltage amplitude of the pin 5 of the second comparator U1B, the duty cycle of the output rectangular wave of the pin 7 of the second comparator U1B gradually increases until the duty cycle of the output rectangular wave of the pin 7 is unchanged after the voltage amplitude of the pin 5 of the second comparator U1B is stabilized, and the process realizes the soft start of the switching power supply. After the soft start of the switching power supply is completed, the adjustable resistor R20 may be adjusted to change the voltage amplitude of the pin 5 of the second comparator U1B, so as to change the duty ratio of the output rectangular wave of the pin 7 of the second comparator U1B, so as to change the voltage magnitude of the output voltage signal Vout of the switching power supply.
It should be noted that the third transistor Q3 may also be an NPN type, and the stable voltage of the fourth capacitor C4 may be determined according to actual conditions through capacitance parameters, which is not limited specifically.
Optionally, the switching power supply further includes a second diode D2, the second diode D2 and the power-on start circuit 100 form a bootstrap circuit, an anode of the second diode D2 is electrically connected to the second pole of the MOS transistor Q8, and a cathode of the second diode D2 is electrically connected to the first pole of the first transistor Q1.
When the MOS transistor Q8 is turned on, the voltage value of the node Vef at the first end of the first capacitor C1 is higher than the voltage value of the output voltage Vout, and the voltage of the node Vef supplies power to the MOS transistor control circuit 120 due to the reverse cut-off of the diode; when the MOS transistor Q8 is turned off, the fourth diode D4 is turned on, the ground terminal of the first capacitor C1 and the SGND are short-circuited, the second diode D2 is turned on, the voltage at the node Vout charges the first capacitor C1, so as to realize the bootstrap of the MOS transistor control circuit 120, and the voltage at the node Vef can indirectly reflect the voltage value of the output voltage signal Vout.
Optionally, the switching power supply further includes a voltage loop circuit 130, the voltage loop circuit 130 includes a fourth transistor Q4, a third diode D3 and a thirteenth resistor R13, a cathode of the third diode D3 is electrically connected to a cathode of the second diode D2 as an input terminal of the voltage loop circuit 130, an anode of the third diode D3 is electrically connected to a base of the fourth transistor Q4 through the thirteenth resistor R13, a first pole of the fourth transistor Q4 is grounded, and a second pole of the fourth transistor Q4 is electrically connected to a second terminal of the adjustable resistor R20 as an output terminal of the voltage loop circuit 130.
Wherein, the third diode D3 is a zener diode, since the voltage at the node Vef can indirectly reflect the voltage value of the output voltage signal Vout, when the voltage value of the voltage Vout is too high, the voltage at the node Vef will also be higher, the voltage at the node Vef is stabilized by the third diode D3, the fourth transistor Q4 is in an amplification state through the thirteenth resistor R13, so that the current flowing through the ninth resistor R9 is reduced, the voltage at the ninth resistor R9 is reduced, the voltage at the ninth resistor R9 is reduced by the voltage at the 5-pin of the second comparator U1B, the duty ratio of the rectangular wave output at the 7-pin of the second comparator U1B is reduced, the duty ratio of the MOS transistor control signal generated by the MOS transistor control circuit 120 is reduced, so as to reduce the voltage value of the output voltage signal Vout, when the voltage value of the output voltage signal Vout is higher, the more NPN type transistor Q8 is flowed, the smaller the current flowing through the resistor R6, the smaller the duty cycle of the MOSFET control signal, thereby achieving the purpose of controlling the voltage value of the output voltage signal Vout.
Optionally, the switching power supply further includes a voltage-reducing circuit 140, the voltage-reducing circuit includes an inductor L, a fourth diode D4, a light-emitting diode D5, and a fifth capacitor C5, a sixth capacitor C6, a fourteenth resistor R14 and a fifteenth resistor R15, wherein the anode of the second diode D2 is electrically connected to the second pole of the MOS transistor Q8 through an inductor L, the second end of the inductor L is electrically connected to the second pole of the MOS transistor Q8 as the input end of the step-down circuit 140, the first end of the inductor L is electrically connected to the anode of the second diode D2 as the output end of the step-down circuit 140, the first end of the inductor L is grounded through the fifth capacitor C5, the sixth capacitor C6 and the fourteenth resistor R14, the first end of the inductor L is electrically connected to the anode of the light emitting diode D5 through the fifteenth resistor R15, the cathode of the light emitting diode D5 is grounded, the second end of the inductor L is electrically connected to the cathode of the fourth diode D4, and the anode of the fourth diode D4 is grounded.
Specifically, the current Iin of the MOS transistor Q8 when it is turned on may be calculated according to the voltage magnitudes of the input voltage signal Vin and the output voltage signal Vout and the maximum output current Iout, for example, when the voltage of the input voltage signal Vin is 31V, the voltage of the output voltage signal Vout is 12V, and the maximum output current Iout is 1A, the duty ratio D of the control signal of the MOS transistor Q8 is 55%, and the efficiency of the switching power supply is 75%, and the current Iin of the MOS transistor Q8 when it is turned on/(Vin × 75%) is 12 × 1/(31 × 0.55 × 0.75) × 0.94A, so when the MOS transistor Q8 is selected, the current may be selected to be greater than 1.2 times Iin. The inductor L ═ Vout ═ (1-D)/(r ═ I in the step-down circuit 140LF), where r is the ripple rate of the output voltage, typically 0.4, ILFor inductive current, in the step-down circuit 140LThe frequency of the control signal of the MOS transistor Q8 is Iout and f.
Optionally, the MOS transistor control circuit 120 includes a fifth transistor Q5, a sixth transistor Q6, a sixteenth resistor R16, and a seventeenth resistor R17, a first pole of the fifth transistor Q5 is used as an input terminal of the MOS transistor control circuit 120, bases of the fifth transistor Q5 and the sixth transistor Q6 are both used as control terminals of the MOS transistor control circuit 120, a second pole of the fifth transistor Q5 is electrically connected to the first pole of the sixth transistor Q6, a second pole of the sixth transistor Q6 is grounded, a first end of the sixteenth resistor R16 is electrically connected to the second pole of the fifth transistor Q5, a second end of the sixteenth resistor R16 is grounded through the seventeenth resistor R17, and a second end of the sixteenth resistor R16 is used as an output terminal of the MOS transistor control circuit 120.
Specifically, when the rectangular wave output by the PWM wave circuit 112 is at a high level, the bases of the fifth triode Q5 and the sixth triode Q6 are both at a high level, if the fifth triode Q5 is an NPN-type triode and the sixth triode Q6 is a PNP-type triode, the fifth triode Q5 turns on the sixth triode Q6 to turn off, the voltage of the power-on start signal VCC makes the gate of the MOS transistor Q8 at a high level through the sixteenth resistor R16, and if the MOS transistor Q8 is an NMOS, the MOS transistor Q8 turns on; when the rectangular wave is at a low level, the bases of the fifth triode Q5 and the sixth triode Q6 are both at a low level, the fifth triode Q5 turns off the sixth triode Q6 to be turned on, and after the gate of the MOS transistor Q8 discharges through the sixth triode Q6 and the seventeenth resistor R17, the MOS transistor Q8 turns off, so that the on-off of the fifth triode Q5 and the sixth triode Q6 is controlled according to the level of the rectangular wave, and a control signal of the MOS transistor Q8 is generated to control the on-off of the MOS transistor Q8. The seventeenth resistor R17 has a current limiting function when the MOS transistor Q8 is switched on, and the resistance value of the seventeenth resistor R17 can be 20 omega, so that the switching-on and switching-off speed of the MOS transistor Q8 is not influenced, and the generation of oscillation voltage can be effectively limited.
It should be noted that the fifth transistor Q5 may also be a PNP transistor, the sixth transistor Q6 may also be an NPN transistor, and the MOS transistor Q8 may be a PMOS, which is not limited specifically.
Optionally, the switching power supply further includes a current loop circuit 150, the current loop circuit includes a seventh transistor Q7, a seventh capacitor C7, an eighteenth resistor R18 and a nineteenth resistor R19, a first end of the eighteenth resistor R18 and a first end of the nineteenth resistor R19 both serve as input ends of the current loop circuit 150 and are electrically connected to the second pole of the MOS transistor Q8, a second end of the eighteenth resistor R18 is grounded, a second end of the nineteenth resistor R19 is electrically connected to the base of the seventh transistor Q7, the base of the seventh transistor Q7 is grounded through the seventh capacitor C7, the first pole of the seventh transistor Q7 is grounded, and the second pole of the seventh transistor Q7 serves as an output end of the current loop circuit 150 and is electrically connected to the output end of the signal generating circuit 110.
When the current value of the input current signal Iin is greater than 0.7A, the voltage across the ninth resistor R9 is 0.7V, the voltage of the input voltage signal VCC is output to the seventh triode Q7 through the tenth resistor R10 and the second comparator U1B, if the seventh triode Q7 is an NPN-type triode, the seventh triode Q7 is turned on, the bases of the fifth triode Q5 and the sixth triode Q6 in the MOS transistor control circuit 120 are both at a low level, the fifth triode Q5 turns off the sixth triode Q6 and turns on, and the gate of the MOS transistor Q8 is at a low level, so that the driving signal of the MOS transistor Q8, i.e., the control signal of the MOS transistor Q8, is zero, i.e., the MOS transistor Q8 is protected when the input current is too large, a seventh capacitor C7 is connected in parallel between the base and the emitter of the seventh triode Q7, and the size of the MOS transistor Q8 is determined according to the size of the input current 18.
It should be noted that the seventh transistor Q7 may also be a PNP transistor, which is not limited herein.
It should be noted that the foregoing is only a preferred embodiment of the present invention and the technical principles applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail with reference to the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the scope of the present invention.

Claims (10)

1. A switching power supply, comprising: MOS pipe still includes:
the power-on starting circuit is used for outputting a power-on starting signal according to the power signal;
the input end of the signal generating circuit is electrically connected with the output end of the power-on starting circuit, and the signal generating circuit is used for generating a PWM signal according to the power-on starting signal;
the MOS tube control circuit comprises an input end of the MOS tube control circuit, an output end of the power-on starting circuit is electrically connected with the output end of the power-on starting circuit, a control end of the MOS tube control circuit is electrically connected with an output end of the signal generating circuit, an output end of the MOS tube control circuit is electrically connected with a grid electrode of the MOS tube, the MOS tube control circuit is used for generating an MOS tube control signal according to the PWM signal, controlling the on-off of the MOS tube, and the MOS tube is conducted and outputs a voltage signal.
2. The switching power supply according to claim 1, wherein the power-on start circuit comprises a first transistor, a second transistor, a first diode, a first capacitor, a first resistor, a second resistor and a third resistor, a first end of the first resistor is used as an input end of the power-on start circuit, a second end of the first resistor is grounded through the first capacitor, a first pole of the first transistor is electrically connected with a second end of the first resistor, a base of the first transistor is electrically connected with a cathode of the first diode through the second resistor, an anode of the first diode is grounded, a first pole of the second transistor is electrically connected with an anode of the first diode, a second pole of the second transistor is grounded, and a base of the second transistor is electrically connected with the second pole of the first transistor through the third resistor, and the second pole of the first triode is used as the output end of the power-on starting circuit.
3. The switching power supply according to claim 2, wherein the signal generating circuit comprises a triangular wave circuit and a PWM wave circuit, an input terminal of the triangular wave circuit and an input terminal of the PWM wave circuit are both used as the input terminals of the signal generating circuit, an output terminal of the triangular wave circuit is electrically connected to the control terminal of the PWM wave circuit, an output terminal of the PWM wave circuit is used as the output terminal of the signal generating circuit, the triangular wave circuit is configured to generate a triangular wave with adjustable frequency, and the PWM wave circuit is configured to generate a PWM wave with corresponding frequency according to the triangular wave.
4. The switching power supply according to claim 3, wherein the triangular wave circuit comprises a second capacitor, a third capacitor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor and a first comparator, a first end of the fourth resistor and a first end of the second capacitor are used as input ends of the triangular wave circuit, a second end of the second capacitor is grounded, a second end of the fourth resistor is electrically connected with a positive input end of the first comparator, an output end of the first comparator is electrically connected with a first end of the fifth resistor, an inverting input end of the first comparator is electrically connected with a second end of the fifth resistor, a second end of the fifth resistor is grounded through the third capacitor, a first end of the sixth resistor is electrically connected with a first end of the fourth resistor, and a second end of the sixth resistor is electrically connected with a first end of the seventh resistor, the second end of the seventh resistor and the first end of the eighth resistor are both electrically connected with the second end of the fourth resistor, the second end of the eighth resistor is grounded, and the second end of the fifth resistor is used as the output end of the triangular wave circuit.
5. The switching power supply according to claim 3, wherein the PWM wave circuit includes an adjustable resistor, a second comparator, a third transistor, a fourth capacitor, a ninth resistor, a tenth resistor, an eleventh resistor, and a twelfth resistor, a reverse input terminal of the second comparator serves as a control terminal of the PWM wave circuit, a forward input terminal of the second comparator is electrically connected to a first terminal of the third transistor, a second terminal of the third transistor is grounded, a base of the third transistor is electrically connected to a first terminal of the adjustable resistor, a second terminal of the adjustable resistor serves as an input terminal of the PWM wave circuit, a second terminal of the adjustable resistor is electrically connected to an adjustable terminal of the adjustable resistor, a first terminal of the ninth resistor is electrically connected to a base of the third transistor, a second terminal of the ninth resistor is grounded, and a first terminal of each of the tenth resistor and the eleventh resistor is electrically connected to a second terminal of the adjustable resistor And a second end of the tenth resistor is electrically connected with a positive input end of the second comparator, a second end of the eleventh resistor is electrically connected with an output end of the second comparator, a first end of the twelfth resistor is electrically connected with a second end of the eleventh resistor, a second end of the twelfth resistor is grounded, a first end of the fourth capacitor is electrically connected with a positive input end of the second comparator, a second end of the fourth capacitor is grounded, and an output end of the second comparator is used as an output end of the PWM wave circuit.
6. The switching power supply according to claim 5, further comprising a second diode, wherein the second diode and the power-on start-up circuit form a bootstrap circuit, an anode of the second diode is electrically connected to the second diode of the MOS transistor, and a cathode of the second diode is electrically connected to the first electrode of the first transistor.
7. The switching power supply according to claim 6, further comprising a voltage loop circuit, wherein the voltage loop circuit comprises a fourth transistor, a third diode and a thirteenth resistor, a negative electrode of the third diode is electrically connected to a negative electrode of the second diode as an input terminal of the voltage loop circuit, a positive electrode of the third diode is electrically connected to a base electrode of the fourth transistor through the thirteenth resistor, a first electrode of the fourth transistor is grounded, and a second electrode of the fourth transistor is electrically connected to a second end of the adjustable resistor as an output terminal of the voltage loop circuit.
8. The switching power supply according to claim 6, further comprising a voltage-reducing circuit, wherein the voltage-reducing circuit comprises an inductor, a fourth diode, a light-emitting diode, a fifth capacitor, a sixth capacitor, a fourteenth resistor and a fifteenth resistor, an anode of the second diode is electrically connected to the second diode of the MOS transistor through the inductor, a second end of the inductor is electrically connected to the second diode of the MOS transistor as an input end of the voltage-reducing circuit, a first end of the inductor is electrically connected to an anode of the second diode as an output end of the voltage-reducing circuit, a first end of the inductor is respectively connected to ground through the fifth capacitor, the sixth capacitor and the fourteenth resistor, a first end of the inductor is electrically connected to the anode of the light-emitting diode through the fifteenth resistor, a cathode of the light-emitting diode is connected to ground, the second end of the inductor is electrically connected with the cathode of the fourth diode, and the anode of the fourth diode is grounded.
9. The switching power supply according to claim 1, wherein the MOS transistor control circuit comprises a fifth transistor, a sixth transistor, a sixteenth resistor and a seventeenth resistor, a first pole of the fifth transistor is used as the input terminal of the MOS transistor control circuit, a base of the fifth transistor and a base of the sixth transistor are both used as the control terminals of the MOS transistor control circuit, a second pole of the fifth transistor is electrically connected to the first pole of the sixth transistor, a second pole of the sixth transistor is grounded, a first end of the sixteenth resistor is electrically connected to the second pole of the fifth transistor, a second end of the sixteenth resistor is grounded through the seventeenth resistor, and a second end of the sixteenth resistor is used as the output terminal of the MOS transistor control circuit.
10. The switching power supply according to claim 1, further comprising a current loop circuit, wherein the current loop circuit comprises a seventh transistor, a seventh capacitor, an eighteenth resistor and a nineteenth resistor, a first end of the eighteenth resistor and a first end of the nineteenth resistor are electrically connected as an input end of the current loop circuit to the second pole of the MOS transistor, a second end of the eighteenth resistor is grounded, a second end of the nineteenth resistor is electrically connected to a base of the seventh transistor, a base of the seventh transistor is grounded through the fifth capacitor, a first pole of the seventh transistor is grounded, and a second pole of the seventh transistor is electrically connected as an output end of the current loop circuit to the output end of the signal generating circuit.
CN202020218466.XU 2020-02-27 2020-02-27 Switch power supply Active CN211701851U (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112953478A (en) * 2021-03-19 2021-06-11 苏州贝昂科技有限公司 Switch controller and electronic equipment

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112953478A (en) * 2021-03-19 2021-06-11 苏州贝昂科技有限公司 Switch controller and electronic equipment

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