Switching power supply circuit and electronic equipment

Abstract

The utility model relates to a switching power supply circuit and electronic equipment. The circuit comprises a power supply input end, a power supply output end, a transformer comprising a primary winding and a secondary winding, a main power switch unit, an active clamping unit, a clamping driving unit, a voltage dividing unit and a built-in MOS control chip. The main power switch unit is connected with the power supply input end, the primary winding and the voltage division unit, and is switched on when receiving voltage division output of the voltage division unit; the voltage dividing unit is connected with the power supply input end and the built-in MOS control chip, and generates divided voltage output when the built-in MOS control chip is switched on; the clamping driving unit is connected with the built-in MOS control chip and generates a first driving level when the clamping driving unit is switched on and generates a second driving level when the clamping driving unit is switched off, and the active clamping unit is connected with the primary winding and the clamping driving unit, is switched off when receiving the first driving level and is switched on when receiving the second driving level. According to the utility model, the loop loading capability and the voltage stress bearing capability can be improved through a simple circuit design.

Description

Technical Field

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

[0002] In the field of modern electronics, switching power supplies have become the mainstream technology in the power supply field due to their advantages such as high efficiency, small size, and light weight. Especially in step-up / step-down power conversion applications in home appliances, industry, and communications, isolated switching power supplies are widely used, with flyback switching power supply circuits being particularly common. In switching power supply design, it is necessary to consider improving conversion power and reducing voltage spike stress on the main power MOSFETs. Utility Model Content

[0003] The technical problem to be solved by this utility model is to provide a switching power supply circuit and electronic device, which addresses the above-mentioned technical defects of the prior art.

[0004] The technical solution adopted by this utility model to solve its technical problem is: to construct a switching power supply circuit, including: a power input terminal, a power output terminal and a transformer including a primary winding and a secondary winding, as well as a main power switching unit, an active clamping unit, a clamping drive unit, a voltage divider unit and a built-in MOS control chip.

[0005] The main power switch unit is connected to the power input terminal, the primary winding of the transformer, and the voltage divider unit, respectively, and is turned on when receiving the voltage divider output of the voltage divider unit, and turned off otherwise.

[0006] The voltage divider unit is connected to the power input terminal and the built-in MOS control chip, and is used to generate the voltage divider output when the built-in MOS control chip is turned on, and to turn off the voltage divider output when the built-in MOS control chip is turned off;

[0007] The clamping drive unit is connected to the built-in MOS control chip and is used to generate a first drive level when the built-in MOS control chip is turned on and a second drive level when the built-in MOS control chip is turned off.

[0008] The active clamping unit is connected to the primary winding of the transformer and the clamping drive unit respectively, and is used to turn off when receiving the first drive level and turn on when receiving the second drive level.

[0009] The secondary winding of the transformer is connected to the power output terminal to provide power output.

[0010] Preferably, in one embodiment of the switching power supply circuit of the utility model, the main power switching unit includes a first MOS transistor;

[0011] The source of the first MOS transistor is connected to the power input terminal, the drain of the first MOS transistor is connected to the first end of the primary winding, and the gate of the first MOS transistor is connected to the voltage divider output terminal of the voltage divider unit.

[0012] Preferably, in one embodiment of the switching power supply circuit of the present invention, the voltage divider unit includes a first resistor and a second resistor;

[0013] The first end of the first resistor is connected to the power input terminal, the second end of the first resistor is connected to the first end of the second resistor and the gate of the first MOS transistor, and the second end of the second resistor is connected to the drain pin of the built-in MOS control chip.

[0014] Preferably, in one embodiment of the switching power supply circuit described in the utility model, the first MOS transistor is a PMOS transistor.

[0015] Preferably, in one embodiment of the switching power supply circuit of the utility model, the active clamping unit includes a first charging capacitor and a second MOS transistor;

[0016] The negative terminal of the first charging capacitor is connected to the first end of the primary winding, the positive terminal of the first charging capacitor is connected to the drain of the second MOS transistor, the source of the second MOS transistor is connected to the second end of the primary winding and grounded, and the gate of the second MOS transistor is connected to the output terminal of the clamping drive unit to receive the drive level output by the clamping drive unit.

[0017] Preferably, in one embodiment of the switching power supply circuit described in the utility model, the second MOS transistor is an NMOS transistor.

[0018] Preferably, in one embodiment of the switching power supply circuit of the utility model, the clamping drive unit includes a first diode, a first transistor, a second charging capacitor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a seventh resistor.

[0019] The anode of the first diode and the first terminal of the third resistor are respectively connected to the source pin of the built-in MOS control chip;

[0020] The cathode of the first diode is connected to the positive terminal of the second charging capacitor and the first terminal of the fifth resistor; the second terminal of the third resistor is connected to the first terminal of the fourth resistor and the first terminal of the seventh resistor; and the second terminal of the seventh resistor is connected to the base of the first transistor.

[0021] The second end of the fifth resistor and the collector of the first transistor are connected to the first end of the sixth resistor, and the second end of the sixth resistor is connected to the active clamping unit;

[0022] The second terminal of the fourth resistor, the negative terminal of the second charging capacitor, and the emitter of the first transistor are grounded.

[0023] Preferably, in one embodiment of the switching power supply circuit of the present invention, the transformer further includes an auxiliary winding; the switching power supply circuit further includes a chip power supply unit;

[0024] The input terminal of the chip power supply unit is connected to the first terminal of the auxiliary winding, the output terminal of the chip power supply unit is connected to the power supply pin of the built-in MOS control chip, and the second terminal of the auxiliary winding is connected to the source pin of the built-in MOS control chip.

[0025] Preferably, in one embodiment of the switching power supply circuit of the utility model, the chip power supply unit includes: a third charging capacitor, a second diode, and an eighth resistor;

[0026] The anode of the second diode is connected to the first end of the auxiliary winding, the cathode of the second diode is connected to the first end of the eighth resistor, the second end of the eighth resistor is connected to the positive terminal of the third charging capacitor and the power supply pin of the built-in MOS control chip, and the negative terminal of the third charging capacitor is connected to the source pin of the built-in MOS control chip.

[0027] The present invention provides an electronic device including the switching power supply circuit described above.

[0028] The switching power supply circuit and electronic device of this utility model have the following beneficial effects: the circuit load capacity and voltage stress resistance are improved through simple circuit design. Attached Figure Description

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0030] Figure 1 This is a logic block diagram of an embodiment of a switching power supply circuit according to the present invention;

[0031] Figure 2 This is a circuit schematic diagram of an embodiment of a switching power supply circuit according to this utility model;

[0032] Figure 3 This is a logic block diagram of another embodiment of the switching power supply circuit of this utility model;

[0033] Figure 4 This is a circuit diagram of another embodiment of the switching power supply circuit of this utility model. Detailed Implementation

[0034] To provide a clearer understanding of the technical features, objectives, and effects of this utility model, the specific embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0035] like Figure 1 The diagram illustrates an embodiment of a switching power supply circuit according to this invention. Figure 1 In one embodiment of the switching power supply circuit of the present invention, the circuit includes: a power input terminal 110, a power output terminal 130, a transformer 120 comprising a primary winding 121 and a secondary winding 122, a main power switching unit 140, an active clamping unit 170, a clamping drive unit 160, a voltage divider unit 180, and a built-in MOS control chip 150. The main power switching unit 140 is connected to the power input terminal 110, the primary winding 121 of the transformer 120, and the voltage divider unit 180, and is used to turn on when receiving the voltage divider output of the voltage divider unit 180, and otherwise remain off. The voltage divider unit 180 is connected to the power input terminal 110 and the built-in MOS control chip 150. Chip 150 generates a voltage divider output when the built-in MOS control chip 150 is turned on and turns off the voltage divider output when the built-in MOS control chip 150 is turned off; clamping drive unit 160 is connected to the built-in MOS control chip 150 and is used to generate a first drive level when the built-in MOS control chip 150 is turned on and a second drive level when the built-in MOS control chip 150 is turned off; active clamping unit 170 is connected to the primary winding 121 of transformer 120 and clamping drive unit 160 respectively, and is used to turn off when receiving the first drive level and turn on when receiving the second drive level; secondary winding 122 of transformer 120 is connected to power output terminal 130 to provide power output.

[0036] Specifically, external power is input to the switching power supply circuit through power input terminal 110. When the main power switching unit 140 is turned on, the voltage is transformed by transformer 120, and power is output at power output terminal 130. During the operation of the switching power supply circuit, the main power switching unit 140 can be switched on or off by turning on or off the built-in MOS control chip 150. Specifically, the MOS control chip 150 controls the voltage divider unit 180 to turn on or off, thereby controlling the voltage divider output of the voltage divider unit 180, and controlling the main power switching unit 140 to turn on through this voltage divider output. For example, when the built-in MOS control chip 150 is turned on, the voltage divider unit 180 is turned on, and the voltage divider unit 180 outputs a divided voltage to the main power switch unit 140, causing the main power switch unit 140 to turn on; when the built-in MOS control chip 150 is turned off, the voltage divider unit 180 turns off, the voltage divider unit 180 turns off the divided voltage output, and the main power switch unit 140 turns off when it does not receive a divided voltage output from the voltage divider unit 180.

[0037] When the main power switching unit 140 is turned on, the primary winding 121 of the transformer 120 is in a reverse-excitation magnetic state. At the same time, when the built-in MOS control chip 150 is turned on, the built-in MOS control chip 150 outputs a control level to control the clamping drive unit 160 to operate. The clamping drive unit 160 outputs a first drive level, and the active clamping unit 170 receives the first drive level and turns off.

[0038] When the main power switching unit 140 is turned off, the primary winding 121 of the transformer 120 is in a flyback demagnetizing state. At this time, the power input terminal 110 no longer provides power input to the primary winding 121 of the transformer 120. Instead, demagnetization is achieved through the secondary winding 122 of the transformer 120, resulting in power output at the power output terminal 130, ultimately providing the power output of the switching power supply circuit. Simultaneously, when the built-in MOS control chip 150 is turned off, its control level output is disabled. At this time, the clamping drive unit 160 outputs a second drive level, and the active clamping unit 170 receives this second drive level and turns on. When the active clamping unit 170 is on, the voltage of the primary winding 121 of the transformer 120 is clamped, and leakage inductance energy is absorbed without loss. Ultimately, the active clamping unit 120 reduces the voltage spike stress during the operation of the main power switching unit 140.

[0039] The on / off state of the built-in MOS control chip 150 can be achieved through the feedback signal it receives. 。 For example, the built-in MOS control chip 150 is configured to reduce the duty cycle during conduction when the received output voltage level is too high, and vice versa when the received output voltage level is too low, thereby achieving steady-state regulation of the circuit. In a specific embodiment, such as... Figure 2 and Figure 4 As shown, the built-in MOS control chip 150 includes a chip U1, which receives a feedback signal and turns on or off according to the feedback signal. This feedback signal can be a loop feedback signal FB, used to obtain the output voltage detection result at the output terminal. In some embodiments, the feedback signal is obtained by sampling the power output terminal 130 through a feedback circuit. Specifically, the feedback circuit can use an optocoupler to provide closed-loop feedback of the output voltage, causing the built-in MOS control chip 150 to generate a corresponding duty cycle drive signal and turn on or off according to the drive signal. The built-in MOS control chip 150 can employ various chips with different parameters. This novel architecture increases the load power of the built-in MOS control chip to adapt to different power range applications. The maximum voltage stress across the built-in MOS control chip 150 is at the power input and does not change with output, effectively avoiding problems caused by voltage stress limitations in the built-in MOS control chip 150.

[0040] Optional, such as Figure 2As shown, the main power switching unit 140 includes a first MOSFET; the source of the first MOSFET is connected to the power input terminal 110, the drain of the first MOSFET is connected to the first end of the primary winding 121, and the gate of the first MOSFET is connected to the voltage divider output terminal of the voltage divider unit 180. In a specific embodiment, the first MOSFET in the main power switching unit 140 is MOSFET S1. MOSFET S1 is turned on or off according to its source-gate voltage difference. Since the source voltage of MOSFET S1 is determined by the power input and is essentially a constant value, the source-gate voltage difference of MOSFET S1 is ultimately determined by the voltage divider output of the voltage divider unit 180. The voltage divider output of the voltage divider unit 180 is determined by the conduction state of the built-in MOSFET control chip 150. In one embodiment, when the built-in MOS control chip 150 is turned on, the voltage divider unit 180 divides the power input to obtain a voltage divider output that is lower than the power input. This power input and the voltage divider output form a source-gate voltage difference for the MOS transistor S1, which can drive the MOS transistor S1 to turn on. When the built-in MOS control chip 150 is turned off, the voltage divider unit 180 does not divide the power input, meaning that no voltage difference can be formed between the source and gate of the MOS transistor S1, and the MOS transistor S1 cannot be driven to turn on and remains off. In a specific application scenario, the MOS transistor S1 can be a PMOS transistor. This setting transfers the main power circuit and maximum voltage stress to an external MOS transistor, ensuring that the control timing remains unchanged while improving the circuit's load-carrying capacity and voltage stress withstand capability.

[0041] Furthermore, the voltage divider unit 180 includes a first resistor and a second resistor; the first end of the first resistor is connected to the power input terminal 110, the second end of the first resistor is connected to the first end of the second resistor and the gate of the first MOSFET, and the second end of the second resistor is connected to the drain pin of the built-in MOSFET control chip 150. In a specific embodiment, the first resistor includes resistor R1, and the second resistor includes resistor R2. When the built-in MOSFET control chip 150 is in the ON state, the power input of the power input terminal 110 is divided by resistors R1 and R2, and a voltage difference is formed between the gate and source of the MOSFET S1 through resistor R1. By reasonably selecting the resistance values ​​of resistors R1 and R2, this voltage difference can be made to be within the gate-source driving range of the MOSFET S1, thereby turning on the MOSFET S1. When the built-in MOSFET control chip 150 is in the OFF state, resistor R1 cannot perform voltage division, that is, there is no voltage difference across resistor R1 that can drive the MOSFET S1 to turn on, and the MOSFET S1 remains OFF.

[0042] Optionally, the active clamping unit 170 includes a first charging capacitor and a second MOSFET. The negative terminal of the first charging capacitor is connected to the first end of the primary winding 121, the positive terminal of the first charging capacitor is connected to the drain of the second MOSFET, the source of the second MOSFET is connected to the second end of the primary winding 121 and grounded, and the gate of the second MOSFET is connected to the output terminal of the clamping drive unit 160 to receive the drive level output by the clamping drive unit 160. In one specific embodiment, the first charging capacitor includes a capacitor C1, and the second MOSFET includes a MOSFET S2. The gate of the MOSFET S2 is turned off when receiving a second drive level and turned on when receiving a first drive level. When the MOSFET S2 is turned on, the leakage inductance energy of the primary winding 121 of the transformer 120 is absorbed through the capacitor C1. In one specific embodiment, the MOSFET S2 is an NMOS transistor.

[0043] Optionally, the clamping drive unit 160 includes a first diode, a first transistor, a second charging capacitor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a seventh resistor; the anode of the first diode and the first terminal of the third resistor are respectively connected to the source pin of the built-in MOS control chip 150; the cathode of the first diode is connected to the positive terminal of the second charging capacitor and the first terminal of the fifth resistor; the second terminal of the third resistor is connected to the first terminal of the fourth resistor and the first terminal of the seventh resistor; the second terminal of the seventh resistor is connected to the base of the first transistor; the second terminal of the fifth resistor and the collector of the first transistor are connected to the first terminal of the sixth resistor; the second terminal of the sixth resistor is connected to the active clamping unit 170; the second terminal of the fourth resistor, the negative terminal of the second charging capacitor, and the emitter of the first transistor are grounded.

[0044] In one specific embodiment, the first diode includes diode D1, the third resistor includes resistor R3, the fourth resistor includes resistor R4, the fifth resistor includes resistor R5, the sixth resistor includes resistor R6, the seventh resistor includes resistor R7, the second charging capacitor includes capacitor C2, and the first transistor includes transistor Q1. When the built-in MOS control chip 150 is turned on, resistors R3 and R4 form a voltage divider. The voltage at the first end of resistor R3 charges capacitor C2 through diode D1, while the voltage at the second end of resistor R3 is input to the base of transistor Q1 through resistor R6, driving transistor Q1 to turn on. When transistor Q1 is in the turned-on state, the collector and emitter potentials of transistor Q1 are close, that is, the collector voltage of transistor Q1 is pulled low. At this time, a first drive level (corresponding to a low level) is output at the second end of resistor R6 to drive the active clamping unit 170 to turn off. When the active clamping unit 170 includes MOSFET S2, the low-level output through resistor R6 drives MOSFET S2 to turn off, and the active clamping unit 170 is in the off state. When the built-in MOSFET control chip 150 is off, the source pin of the built-in MOSFET control chip 150 has no output, and resistors R3 and R4 have no voltage input. At this time, the base of transistor Q1 has no voltage drive and enters the off state. Capacitor C2 begins to discharge, generating a discharge voltage. This discharge voltage outputs a second drive level (corresponding to a high level) at the second end of resistor R6 through resistor R5. This second drive level drives the active clamping unit 170 to conduct. At the same time, diode D1 is used to prevent the discharge voltage of capacitor C2 from entering the source pin of the built-in MOSFET control chip 150. When the active clamping unit 170 includes MOSFET S2, the high-level output through resistor R6 drives MOSFET S2 to conduct, and the active clamping unit 170 is in the conducting state. Here, a transistor is used as the output inverse complementary device, paired with a drive energy storage capacitor, a charging diode, and a current-limiting voltage divider resistor to realize an inverse-time drive circuit. In one embodiment, transistor Q1 is an NPN transistor.

[0045] In another embodiment, such as Figure 3 and Figure 4 As shown, transformer 120 also includes an auxiliary winding 123; the switching power supply circuit also includes a chip power supply unit 190; the input terminal of the chip power supply unit 190 is connected to the first terminal of the auxiliary winding 123, the output terminal of the chip power supply unit 190 is connected to the power supply pin of the built-in MOS control chip 150, and the second terminal of the auxiliary winding 123 is connected to the source pin of the built-in MOS control chip 150. Specifically, the built-in MOS control chip 150 can be powered by the auxiliary winding 123 of transformer 120, that is, the auxiliary winding 123 of transformer 120 provides voltage output to the source pin of the built-in MOS control chip 150 through the chip power supply unit 190.

[0046] Furthermore, the chip power supply unit 190 includes a third charging capacitor, a second diode, and an eighth resistor. The anode of the second diode is connected to the first terminal of the auxiliary winding 123, the cathode of the second diode is connected to the first terminal of the eighth resistor, the second terminal of the eighth resistor is connected to the positive terminal of the third charging capacitor and the power supply pin of the built-in MOS control chip 150, and the negative terminal of the third charging capacitor is connected to the source pin of the built-in MOS control chip 150. In a specific embodiment, the third charging capacitor includes capacitor C3, the second diode includes diode D3, and the eighth resistor includes resistor R8. That is, when the main power switching unit 140 is turned on, the transformer 120 operates, and a voltage is generated across the auxiliary winding 123 of the transformer 120. This voltage supplies power to the power supply pin of the built-in MOS control chip 150 through diode D3 and resistor R3, while simultaneously charging capacitor C3. When the main power switching unit 140 is turned off, there is no voltage output across the auxiliary winding 123 of the transformer 120. At this time, capacitor C3 begins to discharge and supply power to the power supply pin of the built-in MOS control chip 150. At the same time, diode D2 is used to prevent the discharge voltage of capacitor C3 from causing backflow into the auxiliary winding 123 of transformer 120.

[0047] In one embodiment, such as Figure 2 As shown, the built-in MOS control chip 150 can also be powered by a high-voltage power supply.

[0048] Furthermore, one electronic device according to this invention includes the switching power supply circuit described above. During the operation of the electronic device, the switching power supply circuit can supply power to the internal working circuit.

[0049] It is understood that the above embodiments only illustrate preferred embodiments of the present utility model, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present utility model patent. It should be noted that for those skilled in the art, the above technical features can be freely combined, and several modifications and improvements can be made without departing from the concept of the present utility model, all of which fall within the protection scope of the present utility model. Therefore, all equivalent transformations and modifications made within the scope of the claims of the present utility model should fall within the coverage of the claims of the present utility model.

Claims

1. A switching power supply circuit, characterized in that, include: The power input terminal, power output terminal, and transformer including primary and secondary windings, as well as main power switching unit, active clamping unit, clamping drive unit, voltage divider unit, and built-in MOS control chip; The main power switch unit is connected to the power input terminal, the primary winding of the transformer, and the voltage divider unit, respectively, and is turned on when receiving the voltage divider output of the voltage divider unit, and turned off otherwise. The voltage divider unit is connected to the power input terminal and the built-in MOS control chip, and is used to generate the voltage divider output when the built-in MOS control chip is turned on, and to turn off the voltage divider output when the built-in MOS control chip is turned off; The clamping drive unit is connected to the built-in MOS control chip and is used to generate a first drive level when the built-in MOS control chip is turned on and a second drive level when the built-in MOS control chip is turned off. The active clamping unit is connected to the primary winding of the transformer and the clamping drive unit respectively, and is used to turn off when receiving the first drive level and turn on when receiving the second drive level. The secondary winding of the transformer is connected to the power output terminal to provide power output.

2. The switching power supply circuit according to claim 1, characterized in that, The main power switching unit includes a first MOSFET; The source of the first MOS transistor is connected to the power input terminal, the drain of the first MOS transistor is connected to the first end of the primary winding, and the gate of the first MOS transistor is connected to the voltage divider output terminal of the voltage divider unit.

3. The switching power supply circuit according to claim 2, characterized in that, The voltage divider unit includes a first resistor and a second resistor; The first end of the first resistor is connected to the power input terminal, the second end of the first resistor is connected to the first end of the second resistor and the gate of the first MOS transistor, and the second end of the second resistor is connected to the drain pin of the built-in MOS control chip.

4. The switching power supply circuit according to claim 2, characterized in that, The first MOS transistor is a PMOS transistor.

5. The switching power supply circuit according to claim 1, characterized in that, The active clamping unit includes a first charging capacitor and a second MOS transistor; The negative terminal of the first charging capacitor is connected to the first end of the primary winding, the positive terminal of the first charging capacitor is connected to the drain of the second MOS transistor, the source of the second MOS transistor is connected to the second end of the primary winding and grounded, and the gate of the second MOS transistor is connected to the output terminal of the clamping drive unit to receive the drive level output by the clamping drive unit.

6. The switching power supply circuit according to claim 5, characterized in that, The second MOS transistor is an NMOS transistor.

7. The switching power supply circuit according to claim 1, characterized in that, The clamping drive unit includes a first diode, a first transistor, a second charging capacitor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a seventh resistor; The anode of the first diode and the first terminal of the third resistor are respectively connected to the source pin of the built-in MOS control chip; The cathode of the first diode is connected to the positive terminal of the second charging capacitor and the first terminal of the fifth resistor; the second terminal of the third resistor is connected to the first terminal of the fourth resistor and the first terminal of the seventh resistor; and the second terminal of the seventh resistor is connected to the base of the first transistor. The second end of the fifth resistor and the collector of the first transistor are connected to the first end of the sixth resistor, and the second end of the sixth resistor is connected to the active clamping unit; The second terminal of the fourth resistor, the negative terminal of the second charging capacitor, and the emitter of the first transistor are grounded.

8. The switching power supply circuit according to claim 1, characterized in that, The transformer also includes an auxiliary winding; the switching power supply circuit also includes a chip power supply unit. The input terminal of the chip power supply unit is connected to the first terminal of the auxiliary winding, the output terminal of the chip power supply unit is connected to the power supply pin of the built-in MOS control chip, and the second terminal of the auxiliary winding is connected to the source pin of the built-in MOS control chip.

9. The switching power supply circuit according to claim 8, characterized in that, The chip power supply unit includes: a third charging capacitor, a second diode, and an eighth resistor; The anode of the second diode is connected to the first end of the auxiliary winding, the cathode of the second diode is connected to the first end of the eighth resistor, the second end of the eighth resistor is connected to the positive terminal of the third charging capacitor and the power supply pin of the built-in MOS control chip, and the negative terminal of the third charging capacitor is connected to the source pin of the built-in MOS control chip.

10. An electronic device, characterized in that, Includes the switching power supply circuit as described in any one of claims 1 to 9.

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