Switching power supply and electronic device

Abstract

The application discloses a switching power supply and electronic equipment, the switching power supply comprises: an inductor connected between an input voltage and a first node; a capacitor connected between an output voltage and a ground terminal; a main switch tube connected between the first node and the ground terminal, the inductor being charged when the main switch tube is turned on; a synchronous switch tube connected between the output voltage and the first node, comprising a first switch tube and a second switch tube connected in series, the first switch tube being controlled to be turned on or turned off through a second control signal, the inductor being discharged when the first switch tube is turned on; a bias circuit, providing a first bias voltage when the input voltage is less than the output voltage, and providing a second bias voltage when the input voltage is greater than the output voltage, the second switch tube being controlled to be turned on through the first bias voltage and the second bias voltage, and a discharge path being provided for the inductor so that the inductor works in a freewheeling stage. It is guaranteed that the Boost type switching power supply can normally work in a step-down mode and a step-up mode, and the application range of the Boost type switching power supply is widened.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, specifically to a switching power supply and electronic device. Background Technology

[0002] With the rapid development of various portable consumer electronics products, low-voltage, low-power switching power supplies with a wide input voltage range are the current and future development trend. Traditional boost circuits can only achieve voltage boosting, meaning the output voltage is higher than the input voltage, which imposes many limitations in practical applications. For example, when the load requires a voltage range that includes both higher and lower than the input voltage, traditional boost circuits struggle to meet application scenarios where the output voltage is lower than the input voltage.

[0003] Therefore, expanding the voltage range of the Boost circuit can further meet the needs of a wider range of applications. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a Boost-type switching power supply and its electronic device with a wider input voltage range.

[0005] In a first aspect, this application provides a switching power supply, comprising:

[0006] An inductor is connected between the input voltage and the first node;

[0007] The first capacitor is connected between the output voltage and the ground terminal;

[0008] The main switch is connected between the first node and the ground terminal. The main switch is controlled to be turned on or off by a first control signal. When the main switch is turned on, the inductor is charged.

[0009] A synchronous switch is connected between the output voltage and the first node, including a first switch and a second switch connected in series. The first switch is controlled to be turned on or off by a second control signal. When the first switch is turned on, the inductor discharges.

[0010] The bias circuit provides a first bias voltage when the input voltage is less than the output voltage and a second bias voltage when the input voltage is greater than the output voltage. The first bias voltage and the second bias voltage control the second switch to turn on, providing a discharge path for the inductor so that the inductor operates in the freewheeling phase.

[0011] Optionally, when the second switch is turned on by the second bias voltage, it provides an intermediate voltage to the first node, and the intermediate voltage is greater than the input voltage.

[0012] Optionally, the first bias voltage is less than the second bias voltage, and the first bias voltage is a reference low voltage.

[0013] Optionally, when the second switch tube is turned on by the second bias voltage, the second switch tube is equivalent to a resistance, so as to maintain the input voltage greater than the output voltage.

[0014] Optionally, the bias circuit comprises:

[0015] a comparison unit, configured to compare the input voltage and the output voltage, and generate a state signal;

[0016] a bias unit, connected to the comparison unit, configured to generate the first bias voltage or the second bias voltage according to the state signal.

[0017] Optionally, the bias circuit further comprises:

[0018] a selection circuit, connected to the comparison unit, configured to provide the input voltage or the output voltage to the substrate end of the first switch tube and the substrate end of the second switch tube according to the state signal,

[0019] wherein the input voltage is provided to the substrate end of the first switch tube and the substrate end of the second switch tube when the input voltage is greater than the output voltage, and the output voltage is provided to the substrate end of the first switch tube and the substrate end of the second switch tube when the input voltage is less than the output voltage,

[0020] wherein the difference between the intermediate voltage and the input voltage is less than the forward conduction voltage of the body diode in the second switch tube and the forward conduction voltage of the body diode in the first switch tube.

[0021] Optionally, the bias unit comprises:

[0022] a resistance;

[0023] a third switch tube, having a control end connected to the comparison unit to receive the state signal, a first end connected to the control end of the second switch tube, and a second end grounded;

[0024] a fourth switch tube, having a first end grounded via the resistance, a control end connected to the first end of the fourth switch tube, and a second end connected to the input voltage;

[0025] a fifth switch tube, having a control end connected to the control end of the fourth switch tube, a first end grounded, a second end connected to the control end of the second switch tube, and a substrate end connected to the input voltage;

[0026] a current source, having a first end connected to the input voltage and a second end connected to the second end of the fifth switch tube; and

[0027] a second capacitor, a first end of which is connected to the control end of the fourth switch tube and the control end of the fifth switch tube, and a second end of which is grounded.

[0028] Optionally, the selection circuit comprises:

[0029] a sixth switch tube, a control end of which is connected to the comparison unit to receive the state signal, a first end of which is connected to the substrate end of the first switch tube and the substrate end of the second switch tube, and a second end of which is connected to the input voltage;

[0030] a NOT gate, an input end of which is connected to the comparison unit to receive the state signal;

[0031] a seventh switch tube, a control end of which is connected to the output end of the NOT gate, a first end of which is connected to the substrate end of the first switch tube and the substrate end of the second switch tube, and a second end of which is connected to the output voltage.

[0032] Optionally, the main switch tube and the synchronous switch tube are alternately turned on.

[0033] In a second aspect, the present application further provides an electronic device comprising the switching power supply as described above.

[0034] The switching power supply and the electronic device provided by the present application provide different bias voltages to the second switch tube in the boost mode and the buck mode respectively through the bias circuit, so as to control the second switch tube to be turned on, provide a discharge path for the inductor, and make the inductor work in the freewheeling stage. It is guaranteed that the Boost switching power supply can normally work in the buck mode and the boost mode, the power consumption is reduced compared with the prior art, and the application range of the traditional Boost switching power supply is widened.

[0035] It should be noted that the general description above and the detailed description below are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 a circuit schematic diagram of a switching power supply is shown;

[0037] Figure 2 a circuit schematic diagram of another switching power supply is shown;

[0038] Figure 3 a structure schematic diagram of a switching power supply provided by the first embodiment of the present application is shown;

[0039] Figure 4 a structure schematic diagram of a switching power supply provided by the second embodiment of the present application is shown;

[0040] Figure 5 a circuit schematic diagram of a switching power supply provided by the second embodiment of the present application is shown;

[0041] Figure 6a Fig. 2 shows a waveform diagram of the switching power supply in the boost mode according to an embodiment of the present application.

[0042] Figure 6b Fig. 3 shows a waveform diagram of the switching power supply in the buck mode according to an embodiment of the present application. DETAILED DESCRIPTION

[0043] In order to facilitate the understanding of the present disclosure, the present disclosure will be described more fully below in connection with the accompanying drawings. The preferred embodiments of the present disclosure are shown in the drawings. However, the present disclosure can be implemented in different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present disclosure more thorough and comprehensive.

[0044] Figure 1 Fig. 1 shows a circuit schematic diagram of a switching power supply.

[0045] Referring to Figure 1 , the switching power supply 100 is a conventional Boost circuit, including an inductor L, a main switch N1, a synchronous switch P1, a capacitor C1, and a resistor RL. The inductor L is connected between an input voltage VIN and a first node LX. The control end of the main switch N1 receives a first control signal NG, the first end of the main switch N1 is connected with the first node LX, and the second end of the main switch N1 is connected with a ground end. The control end of the synchronous switch P1 receives a second control signal PG1, the first end of the synchronous switch P1 is connected with the first node LX, and the second end of the synchronous switch P1 is connected with an output voltage VOUT. The capacitor C1 is connected between the output voltage VOUT and the ground end. The resistor RL is connected between the output voltage VOUT and the ground end.

[0046] When the main switch N1 is turned on and the synchronous switch P1 is turned off, the input voltage VIN forms a path through the inductor L and the main switch N1 to the ground end to charge the inductor L and store energy. The output voltage VOUT is provided by the capacitor C1. When the main switch N1 is turned off and the synchronous switch P1 is turned on, the current of the inductor L does not suddenly become 0, the inductor L discharges to release energy to charge the capacitor C1, so that the output voltage VOUT is greater than the input voltage VIN. By repeatedly charging and discharging the inductor L, the switching power supply 100 realizes the boost function.

[0047] Figure 2 Fig. 2 shows a circuit schematic diagram of another switching power supply.

[0048] Referring to Figure 2, in order to expand the range of input voltage VIN of the switching power supply 100. The switching power supply 200 adds a low dropout linear regulator LDO to the switching power supply 100 to solve the application scenario where the input voltage is higher than the output voltage. The switching power supply 200 includes an inductor L, a main switch tube N1, a synchronous switch tube P1, a low dropout linear regulator LDO, a capacitor C1, a capacitor C2, and a resistor RL. The inductor L is connected between the input voltage VIN and the first node LX. The control end of the main switch tube N1 receives the first control signal NG, the first end of the main switch tube N1 is connected with the first node LX, and the second end of the main switch tube N1 is connected with the ground end. The control end of the synchronous switch tube P1 receives the second control signal PG1, the first end of the synchronous switch tube P1 is connected with the first node LX, and the second end of the synchronous switch tube P1 is connected with the output voltage VOUT. The capacitor C1 is connected between the first output voltage VOUT1 and the ground end. The low dropout linear regulator LDO is connected between the first output voltage VOUT1 and the second output voltage VOUT2. The capacitor C2 is connected between the second output voltage VOUT2 and the ground end. The resistor RL is connected between the second output voltage VOUT2 and the ground end.

[0049] When the main switch tube N1 is turned on and the synchronous switch tube P1 is turned off, the input voltage VIN forms a path through the inductor L and the main switch tube N1 to the ground end to charge the inductor L and store energy. The first output voltage VOUT1 is provided by the capacitor C1. When the main switch tube N1 is turned off and the synchronous switch tube P1 is turned on, the current of the inductor L does not suddenly become 0, the inductor L discharges to release energy to charge the capacitor C1, so that the first output voltage VOUT1 is greater than the input voltage VIN. By repeatedly charging and discharging the inductor L, the first output voltage VOUT1 of the switching power supply 200 is greater than the input voltage VIN. The input end of the low dropout linear regulator LDO receives the first output voltage VOUT1 and provides the second output voltage VOUT2 which is lower than the first output voltage VOUT1. Then by setting the parameters of the low dropout linear regulator LDO, the second output voltage VOUT2 is lower than the input voltage VIN. In summary, the switching power supply 200 can not only make the output voltage (the first output voltage VOUT1) greater than the input voltage VIN, but also satisfy the output voltage (the second output voltage VOUT2) less than the input voltage VIN. In turn, it expands the input voltage range of the Boost type switching power supply 200, which can realize both step-up and step-down functions.

[0050] However, whether the switching power supply 200 is in the working state where the input voltage is higher than the output voltage or the working state where the input voltage is lower than the output voltage, the low dropout linear regulator LDO in it is always in the working state, which increases the power loss and in turn reduces the efficiency and limits the application range.

[0051] The application provides a Boost type switching power supply, which can meet application scenarios of input voltage being higher than output voltage and application scenarios of input voltage being lower than output voltage. The switching transistor provided by the application reduces power consumption and improves efficiency in the application scenario of input voltage being lower than output voltage, and the circuit is simple and has strong realizability, thereby effectively widening the input voltage range and load application range of the Boost type switching power supply.

[0052] Figure 3 A structure schematic diagram of a switching power supply provided by the first embodiment of the application is shown. Figure 4 A structure schematic diagram of a switching power supply provided by the second embodiment of the application is shown.

[0053] Referring to Figure 3 The switching power supply 300 comprises a main circuit 310 and a bias circuit 320.

[0054] The main circuit 310 comprises an inductor L, a main switching transistor N1, a synchronous switching transistor 311 and a first capacitor C1. The inductor L is connected between an input voltage VIN and a first node LX. The main switching transistor N1 is connected between the first node LX and a ground terminal, and the main switching transistor N1 is controlled to be turned on or turned off by a first control signal NG, and the inductor L is charged when the main switching transistor N1 is turned on. The synchronous switching transistor 311 is connected between an output voltage VOUT and the first node LX, and comprises a first switching transistor P1 and a second switching transistor P2 connected in series, the first switching transistor P1 is controlled to be turned on or turned off by a second control signal PG1, and the inductor L is discharged when the first switching transistor P1 is turned on.

[0055] The bias circuit 320 provides a bias voltage PG2 to provide a discharge path for the inductor L under different input and output conditions, so that the inductor L works in a freewheeling stage. Further, the bias circuit 320 provides a first bias voltage when the input voltage VIN is less than the output voltage VOUT, and provides a second bias voltage when the input voltage VIN is greater than the output voltage VOUT. Thus, the switching power supply 300 can work in a state of the input voltage VIN being higher than the output voltage VOUT and a state of the input voltage VIN being lower than the output voltage VOUT.

[0056] Further, the substrate end of the first switching transistor P1 and the substrate end of the second switching transistor P2 receive, for example, a high voltage, so that in the state of the input voltage VIN being higher than the output voltage VOUT and the state of the input voltage VIN being lower than the output voltage VOUT, the body diode inside the first switching transistor P1 and the body diode inside the second switching transistor P2 are both reverse biased, thereby protecting the first switching transistor P1 and the second switching transistor P2 in the freewheeling stage, and further avoiding damage to the synchronous switching transistor 311.

[0057] Further, a first end of the main switch N1 is connected to the first node LX, a second end of the main switch N1 is connected to a ground terminal, and a control end of the main switch N1 receives a first control signal NG. A substrate end of the main switch N1 is connected to the second end of the main switch N1. A first end of the second switch P2 is connected to the first node LX, and a control end of the second switch P2 is connected to the bias circuit 320 to receive a bias voltage PG2. A second end of the second switch P2 is connected to a first end of the first switch P1, a second end of the first switch P1 is connected to an output voltage VOUT, and a control end of the first switch P1 receives a second control signal PG1. Further, the main circuit 310 further includes a resistor RL connected between the output voltage VOUT and the ground terminal.

[0058] Further, when the input voltage VIN is greater than the output voltage VOUT, the second switch P2 provides an intermediate voltage to the first node LX when the second switch P2 is turned on by the second bias voltage. The intermediate voltage is greater than the input voltage VIN, so that a discharge path can be formed in the freewheeling phase, thereby ensuring that the switching power supply 300 can work normally in the freewheeling phase, and realizing normal working of the Boost switching power supply when the input voltage VIN is higher than the output voltage VOUT. Further, the difference between the intermediate voltage and the voltage provided to the substrate end of the second switch P2 is less than the forward conduction voltage of the body diode in the second switch P2 and the forward conduction voltage of the body diode in the first switch P1.

[0059] Further, the first bias voltage is less than the second bias voltage, and the first bias voltage is a reference low voltage. Further, when the second switch P2 is controlled by the first bias voltage, the second switch P2 works in a switching state, and when the second switch P2 is controlled by the second bias voltage, the second switch P2 is equivalent to an active resistor, so as to maintain the input voltage VIN greater than the output voltage VOUT.

[0060] Further, the bias circuit 320, for example, includes a comparison unit and a bias unit. The comparison unit is used to compare the input voltage VIN and the output voltage VOUT, and generate a state signal representing the size relationship between the input voltage VIN and the output voltage VOUT. The bias unit is connected to the comparison unit, and generates the first bias voltage or the second bias voltage according to the state signal.

[0061] In other examples, referring to Figure 4The switching power supply 400 further comprises a selection circuit 430 based on the switching power supply 300. The selection circuit 430 receives the output voltage VOUT and the input voltage VIN, and is connected with the comparison unit in the bias circuit 320, and provides the input voltage VIN or the output voltage VOUT to the substrate end of the first switch tube P1 and the substrate end of the second switch tube P2 according to the state signal. Further, the input voltage VIN is provided to the substrate end of the first switch tube P1 and the substrate end of the second switch tube P2 when the input voltage VIN is greater than the output voltage VOUT, and the output voltage VOUT is provided to the substrate end of the first switch tube P1 and the substrate end of the second switch tube P2 when the input voltage VIN is less than the output voltage VOUT. Wherein, the difference between the intermediate voltage and the input voltage VIN is less than the positive conduction voltage of the body diode in the second switch tube P2 and the positive conduction voltage of the body diode in the first switch tube P1, thereby avoiding the body diode of the second switch tube P2 and the body diode of the first switch tube P1 being positively biased in the freewheeling stage.

[0062] Figure 5 A circuit schematic diagram of a switching power supply according to the second embodiment of the present application is shown. Figure 6a A waveform schematic diagram of the switching power supply in the boost mode according to the embodiment of the present application is shown. Figure 6b A waveform schematic diagram of the switching power supply in the boost mode according to the embodiment of the present application is shown.

[0063] Referring to Figure 5 The circuit structure of the main circuit 210 in the switching power supply 400 can be seen from the description of Figure 3 , which will not be described here again.

[0064] The main circuit biasing circuit 320 in the switching power supply 400 comprises a comparison unit 321 and a biasing unit 322. The comparison unit 321 comprises a comparator U1, a first input end of which receives the output voltage VOUT, a second input end of which receives the input voltage VIN, and an output end of which outputs a state signal PSEL. Further, the first input end is, for example, a positive input end of the comparator U1, and the second input end is, for example, a negative input end of the comparator U1. The biasing unit 322 comprises a resistor R1, a second capacitor C2, a third switch tube N2, a fourth switch tube P3, a fifth switch tube P4, and a current source I1. A control end of the third switch tube N2 is connected to the comparison unit 320 to receive the state signal PSEL, a first end of the third switch tube N2 is connected to a control end of the second switch tube P2, and a second end of the third switch tube N2 is grounded. A first end of the fourth switch tube P3 is grounded via the resistor R1, a control end of the fourth switch tube P3 is connected to the first end of the fourth switch tube P3, and a second end of the fourth switch tube P3 is connected to the input voltage VIN. A control end of the fifth switch tube P4 is connected to the control end of the fourth switch tube P3, a first end of the fifth switch tube P4 is grounded, a second end of the fifth switch tube P4 is connected to the control end of the second switch tube P2, and a substrate end is connected to the input voltage VIN. A first end of the current source I1 is connected to the input voltage VIN, and a second end of the current source I1 is connected to the second end of the fifth switch tube P4. A first end of the second capacitor C2 is connected to the control end of the fourth switch tube P3 and the control end of the fifth switch tube P4, and a second end of the second capacitor C2 is grounded. The substrate end of the third switch tube N2 is connected to the second end of the third switch tube N2, and the substrate end of the fourth switch tube P3 is connected to the second end of the fourth switch tube P3.

[0065] The selection circuit 430 of the switching power supply 400 comprises a sixth switch tube P5, a NOT gate U2, and a seventh switch tube P6. A control end of the sixth switch tube P5 is connected to the comparison unit 321 to receive the state signal PSEL, a first end of the sixth switch tube P5 is connected to a substrate end of the first switch tube P1 and a substrate end of the second switch tube P2, and a second end of the sixth switch tube P5 is connected to the input voltage VIN. An input end of the NOT gate U2 is connected to the comparison unit 321 to receive the state signal PSEL. A control end of the seventh switch tube P6 is connected to an output end of the NOT gate U2, a first end of the seventh switch tube P6 is connected to the substrate end of the first switch tube P1 and the substrate end of the second switch tube P2, and a second end of the seventh switch tube P6 is connected to the output voltage VOUT. The substrate end of the sixth switch tube P5 is connected to the second end of the sixth switch tube P5, and the substrate end of the seventh switch tube P6 is connected to the second end of the seventh switch tube P6.

[0066] It should be noted that the above-mentioned switch tubes are, for example, MOS transistors, the control end of the switch tube is the gate of the MOS transistor, the first end of the switch tube is the drain of the MOS transistor, and the second end of the switch tube is the source of the MOS transistor.

[0067] Further, referring to Figure 6a For the switching power supply 400 to work in the boost mode, i.e. the output voltage VOUT is greater than the input voltage VIN. The state signal PSEL outputted by the comparison unit 321 is, for example, high level, the third switch N2 in the bias unit 322 is turned on to make the bias voltage PG2 provided to the second switch PG2 be the reference low voltage (the first bias voltage). The sixth switch P5 in the selection circuit 430 is turned off and the seventh switch P6 is turned on to provide the output voltage VOUT to the substrate end of the first switch P1 and the substrate end of the second switch P2. When the first control signal NG is in the active level state (e.g. high level) and the second control signal PG1 is in the inactive level state (e.g. high level), the main switch N1 in the main circuit 310 is turned on and the first switch P1 is turned off, and the input voltage VIN charges the inductor L. When the first control signal NG is in the inactive level state (e.g. low level) and the second control signal PG1 is in the active level state (e.g. low level), the main switch N1 in the main circuit 310 is turned off and the first switch P1 is turned on, and the second switch P2 is turned on to provide a discharge path for the inductor L.

[0068] Further, referring to Figure 6bIn the step-down mode, the output voltage VOUT is less than the input voltage VIN. The state signal PSEL outputted by the comparison unit 321 is, for example, low level. The third switch N2 in the bias unit 322 is off, the fourth switch P3 is on, and the fifth switch P4 is on, so as to provide the bias voltage PG2=VIN-VSGP3+VSGP4 (second bias voltage) to the second switch PG2. The VSGP3 is the source-gate voltage of the fourth switch P3, and the VSGP4 is the source-gate voltage of the fifth switch P4. The second bias voltage is determined by the resistance R1, the fourth switch P3, the fifth switch P4, and the current mirror I1. The sixth switch P5 in the selection circuit 430 is on, and the seventh switch P6 is off, so as to provide the input voltage VIN to the substrate end of the first switch P1 and the substrate end of the second switch P2, thereby preventing the body diode in the first switch P1 and the body diode in the second switch P2 from being reverse biased and being damaged. When the first control signal NG is in the active level (for example, high level), the second control signal PG1 is in the inactive level (for example, high level), the main switch N1 in the main circuit 310 is on, and the first switch P1 is off, so as to charge the inductor L with the input voltage VIN. When the first control signal NG is in the inactive level (for example, low level), the second control signal PG1 is in the active level (for example, low level), the main switch N1 in the main circuit 310 is off, the first switch P1 is on, and the second switch P2 is on, so as to provide a discharge path for the inductor L. Further, the second switch P2 is controlled to be on according to the second bias voltage, and provides an intermediate voltage at the first node LX, wherein the intermediate voltage =VIN-VSGP3+VSGP4+|VTH_P2|, and the VTH_P2 is the threshold voltage of the second switch P2. In the working condition that the input voltage VIN is greater than the output voltage VOUT, the volt-second balance working principle must be met to realize the freewheeling stage. Further, the intermediate voltage is greater than the input voltage VIN by adjusting the parameters of the components in the bias unit 322, so as to realize the discharge path in the freewheeling stage, and ensure that the switching power supply 400 can work normally in the freewheeling stage. Further, the intermediate voltage provided to the first node LX is higher than the input voltage VIN by adjusting the resistance value of the resistance R1. Further, it is also necessary to ensure that the body diode in the first switch P1 and the body diode in the second switch P2 are reverse biased, that is, the voltage difference between the intermediate voltage and the input voltage (-VSGP3+VSGP4+|VTH_P2|) should be lower than the forward conduction voltage of the body diode in the second switch P2 and the forward conduction voltage of the body diode in the first switch P1.

[0069] Further, the main switch tube N1 and the synchronous switch tube 311 in the switching power supply 400 are alternately turned on. The application provides a switching power supply based on a Boost circuit architecture, in different working states, different bias voltages are provided to the control end of the second switch tube P2, thereby ensuring that the Boost type switching power supply can work normally in the boost (input voltage VIN is less than output voltage VOUT) or buck (input voltage VIN is greater than output voltage VOUT) working state. Further, different voltages are provided to the substrate end of the synchronous switch tube through the selection circuit to avoid the body diode of the synchronous switch tube 311 being biased in the boost or buck working state of the Boost type switching power supply, and damaging the synchronous switch tube 311.

[0070] The application also provides an electronic device comprising the switching power supply provided above.

[0071] It should be noted that the numerical values herein are only used for illustrative description, and in other embodiments of the present disclosure, other numerical values can also be used to implement the present scheme, and the specific setting should be reasonable according to the actual situation, and the present disclosure does not limit this.

[0072] Finally, it should be noted that: obviously, the above embodiments are only examples for clearly illustrating the present disclosure, and are not limitations of the embodiments. For those skilled in the art, on the basis of the above description, other different forms of changes or variations can also be made. Here, it is not necessary and impossible to enumerate all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present disclosure.

[0073] It should also be understood that the terms and expressions used herein are only used for description, and one or more embodiments of the present disclosure should not be limited to these terms and expressions. The use of these terms and expressions does not mean the exclusion of any equivalent features, and it should be recognized that various modifications that can exist should also be included in the scope of the claims. Other modifications, changes and replacements can also exist. Accordingly, the claims should be considered to cover all these equivalents.

Claims

1. A switching power supply, characterized in that, include: An inductor is connected between the input voltage and the first node; The first capacitor is connected between the output voltage and the ground terminal; The main switch is connected between the first node and the ground terminal. The main switch is controlled to be turned on or off by a first control signal. When the main switch is turned on, the inductor is charged. A synchronous switch is connected between the output voltage and the first node, including a first switch and a second switch connected in series. The first switch is controlled to be turned on or off by a second control signal. When the first switch is turned on, the inductor discharges. The bias circuit provides a first bias voltage when the input voltage is less than the output voltage and a second bias voltage when the input voltage is greater than the output voltage. The first and second bias voltages control the second switching transistor to turn on, providing a discharge path for the inductor so that the inductor operates in the freewheeling phase. The bias circuit includes: The comparison unit compares the input voltage and the output voltage and generates a status signal; A biasing unit, connected to the comparison unit, generates either the first bias voltage or the second bias voltage based on the state signal. The biasing unit includes: resistance; The third switch has its control terminal connected to the comparison unit to receive the status signal, its first terminal connected to the control terminal of the second switch, and its second terminal grounded. The fourth switching transistor has its first terminal grounded via the resistor, its control terminal connected to the first terminal of the fourth switching transistor, and its second terminal connected to the input voltage. The fifth switch has its control terminal connected to the control terminal of the fourth switch, its first terminal grounded, its second terminal connected to the control terminal of the second switch, and its substrate terminal connected to the input voltage. A current source, with its first terminal connected to the input voltage and its second terminal connected to the second terminal of the fifth switching transistor; The second capacitor has its first end connected to the control terminals of the fourth and fifth switching transistors, and its second end grounded.

2. The switching power supply according to claim 1, characterized in that, When the second switch is turned on by the second bias voltage, it provides an intermediate voltage to the first node, and the intermediate voltage is greater than the input voltage.

3. The switching power supply according to claim 1, characterized in that, The first bias voltage is less than the second bias voltage, and the first bias voltage is a reference low voltage.

4. The switching power supply according to claim 3, characterized in that, When the second switch is turned on by the second bias voltage, it is equivalent to a resistor to maintain the input voltage greater than the output voltage.

5. The switching power supply according to claim 2, characterized in that, Also includes: A selection circuit, connected to the comparison unit, provides the input voltage or the output voltage to the substrate terminals of the first and second switching transistors according to the status signal. Specifically, when the input voltage is greater than the output voltage, the input voltage is provided to the substrate terminals of the first switching transistor and the second switching transistor; when the input voltage is less than the output voltage, the output voltage is provided to the substrate terminals of the first switching transistor and the second switching transistor. The difference between the intermediate voltage and the input voltage is less than the forward conduction voltage of the body diode in the second switch and the forward conduction voltage of the body diode in the first switch.

6. The switching power supply according to claim 5, characterized in that, The selection circuit includes: The sixth switch has a control terminal connected to the comparison unit to receive the status signal, a first terminal connected to the substrate terminals of the first switch and the second switch, and a second terminal connected to the input voltage. The NOT gate's input is connected to the comparison unit to receive the status signal; The seventh switch has its control terminal connected to the output terminal of the NOT gate, its first terminal connected to the substrate terminals of the first and second switches, and its second terminal connected to the output voltage.

7. The switching power supply according to claim 1, characterized in that, The main switch and the synchronous switch are turned on alternately.

8. An electronic device, characterized in that, Includes the switching power supply according to any one of claims 1-7.

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