Driving circuit, power supply and method thereof

Abstract

The invention relates to a driving circuit, a power supply and a method thereof. A drive circuit (100) for a power supply, the power supply comprising a transformer (T), the drive circuit (100) being arranged on a secondary side (T2) of the transformer (T), the drive circuit (100) comprising: a high-voltage module (20) and a low-voltage module (10), the high-voltage module (20) comprising: a MOSFET switch (22) and a sampling and power module (24); wherein the low-voltage module (10) comprises a detection module (14), a driver (16) and a control logic (12), the detection module (14) comprises a first comparison module (142), and the control logic (12) is configured to generate a switching signal for turning on or turning off the MOSFET switch (22) based on a comparison result of the first comparison module (142).

Description

Technical Field

[0001] The present disclosure relates to power supplies having transformers, and more particularly to drive circuits for power supplies. Background Art

[0002] The power supply has higher and higher requirements for operating frequency and energy efficiency. In traditional power supplies, diodes are usually used as freewheeling diodes on the secondary side of the transformer, but the power consumption of diodes is relatively high. As an example, the common diode conduction voltage drop is around 0.7V. When the power supply system works under high current conditions, its energy conversion efficiency will also be greatly reduced. Such energy efficiency is unacceptable in low-voltage and high-current charging fields such as mobile phones. In addition, the use of diodes will lead to serious heat dissipation problems. The excessive voltage drop of the diode increases the loss of the power supply system during the voltage conversion process, and the temperature rise of the device is higher. For environments with limited volume, system heat dissipation will be a great challenge.

[0003] It has been proposed to use a MOSFET with low on-resistance to replace the diode on the secondary side of the transformer. However, in some high-voltage output application scenarios, the MOSFET on the secondary side will be subjected to high voltage, which places higher requirements on the withstand voltage of the MOSFET and the withstand voltage of the power module inside the driver chip. Summary of the invention

[0004] An object of the present disclosure is to provide a driving circuit for a power supply, a power supply and a method for operating a power supply, aiming to solve one or more of the above-mentioned problems and other potential problems.

[0005] A first aspect of the present disclosure provides a driving circuit for a power supply. The power supply includes a transformer, the driving circuit is arranged on the secondary side of the transformer, the driving circuit includes: a high voltage module that tolerates a first voltage and a low voltage module that tolerates a second voltage, wherein the second voltage is lower than the first voltage, the high voltage module includes: a MOSFET switch, the drain of the MOSFET switch is connected to a switch node; and a sampling and power supply module, which is configured to sample the voltage at the switch node and is configured to provide a power supply voltage to the low voltage module; the low voltage module includes a detection module, a driver and control logic, wherein the detection module includes a first comparison module, the first comparison module is configured to compare the sampled voltage with a first predetermined threshold voltage, and output the comparison result to the control logic; wherein the control logic is configured to generate a switch signal for turning on or off the MOSFET switch based on the comparison result; wherein the driver is configured to drive the MOSFET switch to turn on or off based on the switch signal.

[0006] According to the drive circuit disclosed in the present invention, by providing two different voltage domain modules, in the high-voltage domain, an adaptive power supply and sampling circuit module is added to the MOSFET used as a switch, which is used to bear the high voltage in the application and convert the high voltage into a low voltage to provide it to the low-voltage domain. In the process of high-low voltage conversion, the heat generated by the large voltage drop is dissipated by itself and will not be conducted to the low-voltage domain. According to the present invention, not only can the existence of a high-voltage interface in the drive circuit of the low-voltage domain be avoided, but also the disturbance caused by the high-voltage to low-voltage conversion process can be avoided, the heat dissipation and circuit design complexity are reduced, the area and power consumption of the entire drive circuit are further reduced, the heat dissipation effect is improved, and the power density and reliability of the drive circuit are greatly improved.

[0007] In some embodiments, the switch node is adapted to be connected to a load capacitor, and when the primary side of the transformer is turned off, the inductor current at the secondary side of the transformer charges the load capacitor through the body diode of the MOSFET switch.

[0008] In some embodiments, the sampling and power supply module includes a buck circuit configured to utilize the voltage at the switch node as a voltage source for powering the high voltage module and reduce it to the supply voltage for powering the low voltage module.

[0009] In some embodiments, the low voltage module includes a second comparison module, which is configured to compare the supply voltage with a second predetermined threshold voltage and generate a control logic enable signal in response to the supply voltage being greater than the second predetermined threshold voltage, wherein the enable signal allows the control logic to operate.

[0010] In some embodiments, the high voltage module and the low voltage module use a common ground electrode.

[0011] In some embodiments, the source of the MOSFET switch is grounded.

[0012] In some embodiments, the sampling and power module includes a sampling circuit configured to sample a sample voltage at the switch node and output the sample voltage to the low voltage module.

[0013] In some embodiments, the sampling circuit is configured to determine a voltage difference between a drain and a source of the MOSFET switch and use the voltage difference as the sampled voltage.

[0014] In some embodiments, the first voltage is in the range of 50V to 160V, and / or the second voltage is in the range of 5V to 10V.

[0015] A second aspect of the present disclosure provides a power supply, which may include: a transformer; and a drive circuit according to any one of the first aspects, arranged at a secondary side of the transformer.

[0016] The third aspect of the present disclosure provides a method for operating a power supply according to the second aspect. The method may include: turning on the primary switch of the transformer to charge the primary side of the transformer; turning off the primary switch of the transformer to transfer the primary energy of the transformer to the secondary side of the transformer; using the body diode of the MOSFET switch for freewheeling to charge the load capacitor; collecting the drain voltage of the MOSFET switch; in response to the drain voltage being greater than a predetermined threshold voltage, outputting a control logic enable signal to allow the control logic of the low-voltage module to operate; the control logic controls the MOSFET switch to turn on or off based on the drain voltage.

[0017] According to the driving circuit, power supply and method disclosed in the present invention, heat dissipation and circuit design complexity are reduced by providing two modules with different voltage domains, further reducing the area and power consumption of the entire driving circuit, improving its heat dissipation effect, and greatly improving the power density and reliability of the driving circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and advantages of the embodiments of the present disclosure will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present disclosure are shown by way of example and not limitation.

[0019] Figure 1 An overall schematic diagram of a power supply according to an embodiment of the present disclosure is shown.

[0020] Figure 2 A schematic diagram of implementing a driving circuit according to a first embodiment of the present disclosure is shown.

[0021] Figure 3 A schematic diagram of implementing a driving circuit according to a second embodiment of the present disclosure is shown.

[0022] Figure 4 A flow chart of a method for operating a power supply according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0023] Unless otherwise indicated, corresponding numbers and symbols in different figures generally refer to corresponding module domains. The accompanying drawings are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale. The edges of features drawn in the accompanying drawings do not necessarily represent the end of the feature range.

[0024] References to "one embodiment" or "an implementation" in the framework of this specification are intended to indicate that a particular configuration, structure, or characteristic described with respect to the embodiment is included in at least one embodiment. Therefore, phrases such as "in an embodiment," "in one embodiment," etc., which may appear in various aspects of this specification, do not necessarily refer to exactly the same embodiment. Furthermore, particular configurations, structures, or characteristics may be combined in any appropriate manner in one or more embodiments.

[0025] Figure 1 1 shows an overall schematic diagram of a power supply of an embodiment of the present disclosure. Figure 1 As shown, the power supply includes a transformer T. The transformer T includes a primary coil (referred to as the primary) T1 and a secondary coil (referred to as the secondary) T2. On the primary side T1, a control circuit (not shown) for controlling the charging of the primary coil T1 is also provided. Figure 1 As shown, on the secondary side, a driving circuit 100 is provided, and the driving circuit may include a MOSFET switch 22 and a corresponding circuit for controlling the MOSFET switch 22 to selectively turn on or off (see later). Figure 2 Detailed description). The driving circuit 100 may include a switch node SW, and the switch node SW may be connected to the drain of the MOSFET switch 22. The switch node SW may be connected to a load capacitor 200, and a negative terminal of the load capacitor 200 is grounded, and a positive terminal is connected to the switch node SW. The load capacitor 200 may be connected in parallel with a load 300. Figure 1 As shown, the load 300 is connected in parallel with the load capacitor 200 at the output node VOUT. The driving circuit 100 may include a power supply node VSS and a ground node VDD. A voltage stabilizing capacitor may be provided between the power supply node VSS and the ground node VDD. In some embodiments, the driving circuit 100 may be implemented in the form of an integrated circuit.

[0026] As described in the background technology section, in a conventional power supply, the position where the drive circuit 100 is located is usually replaced by a freewheeling diode. However, the freewheeling diode has large power consumption and large heat dissipation performance. In some schemes, it is proposed to replace the freewheeling diode with a MOSFET switch with low on-resistance, but how to control and drive the MOSFET switch is the key to this technology. However, as the on-resistance of the MOSFET decreases, the overall area and junction capacitance will increase accordingly. Therefore, in order to ensure the conduction of the MOSFET, the control signal output by the driver chip to the MOSFET needs to be sufficiently strong to ensure that the MOSFET is fully turned on.

[0027] In order to ensure that the MOSFET is driven sufficiently, the driver chip must select a process with a very high withstand voltage and also have a low-voltage driving capability. This requirement greatly increases the complexity of designing and producing driver chips. The common circuit design method designs a linear voltage regulator circuit (Low dropout regulator, LDO) inside the chip to drive the gate of the MOSFET through the low voltage provided by the LDO. However, since the parasitic capacitance area of ​​the MOSFET is large, the signal that controls its switch requires a sufficiently large driving capability, so the high-voltage NMOS area used inside the chip will be very large, so the parasitic capacitance of the device will be very large, which will affect the control accuracy and switching frequency. On the other hand, in order to cope with the scenario of driving different MOSFETs, the output current fluctuation range of the LDO is very large, and in the design of the LDO circuit, the change of the load current will affect the relative position of the main pole and the secondary pole of the LDO internal circuit, thereby affecting the stability of the LDO feedback loop, which has high requirements for the loop compensation design and greatly increases the complexity of the driver integrated circuit design. According to the present disclosure, a circuit that can drive MOSFET at high frequency without using LDO is proposed, which can effectively solve the various problems faced by traditional technologies.

[0028] Figure 2 FIG. 2 shows a schematic diagram of a driving circuit 200 according to a first embodiment of the present disclosure. Figure 2 As shown, the driving circuit 100 includes a high voltage module 20 that withstands a first voltage and a low voltage module 10 that withstands a second voltage lower than the first voltage. The high voltage module 20 includes a MOSFET switch 22 and a sampling and power supply module 24. The sampling and power supply module 24 is configured to sample the voltage at the switch node SW or the drain of the MOSFET switch 22 and supply power to the low voltage module 10. The low voltage module 10 includes a control logic 12. The control logic 12 is configured to generate a switch signal for turning on or off the MOSFET switch 22 based on the sampled voltage.

[0029] According to the present disclosure, by dividing the driving circuit into a high-voltage domain and a low-voltage domain that are isolated from each other and can withstand different voltages, the circuits related to the on and off control of the MOSFET switch 22 are set in the low-voltage domain, thereby greatly simplifying the design difficulty of the driving chip. In some embodiments, the circuit process of the high-voltage domain or the high-voltage module can withstand a voltage in the range of 50V~160V, for example, 60V, 70V, 80V, 90V, 100V or other voltage values; the circuit process of the low-voltage domain or the low-voltage module can withstand a voltage in the range of 5~10V, for example, 5V, 6V, 7V, 8V or other voltage values. Considering that the chip design methods, design ideas and circuit processes of the high-voltage domain and the low-voltage domain are different, the design difficulty of the driving chip is greatly simplified.

[0030] In the traditional circuit that uses LDO to drive MOSFET, although the circuit can improve the driving ability of the MOSFET gate of the driver chip and generate a voltage with high precision, its circuit structure is complex, the production cost is high, and the loop compensation is complex. In addition, since the detection, logic and driving circuits of the LDO and the driver chip are integrated together, the heating effect of the circuit will affect other functions of the driver chip, and even cause abnormal working state of the MOSFET at high temperature. The distinction between the high voltage domain and the low voltage domain according to the present disclosure can effectively solve the above technical problems.

[0031] In some embodiments, the high voltage module 20 and the low voltage module 10 use a common ground electrode VSS. In some embodiments, the source electrode S of the MOSFET switch 22 is grounded.

[0032] In some embodiments, Figure 2 As shown, the sampling and power supply module 24 may include a step-down circuit 244, which is configured to use the voltage at the switch node SW as a voltage source for powering the high voltage module 20 and reduce it to a power supply voltage VDD for powering the low voltage module 10. When the transformer T is in operation, the primary control circuit controls the primary switch to be turned on, and the primary coil begins to charge. In the illustrated embodiment, the upper end voltage is a high level, and the lower end voltage is a ground level 0V. After the primary switch is turned on for a period of time, the primary switch is disconnected, and the secondary coil of the transformer is charged according to the electromagnetic induction principle. In the illustrated embodiment, its terminal voltage is a ground level 0V, and the lower end voltage is a high level. At this time, the secondary inductor current charges the load capacitor 200 through the body diode 222 of the MOSFET switch 22. The positive electrode of the load capacitor 200 is connected to the switch node SW and to the drain of the MOSFET switch 22, so the switch node SW, the drain of the MOSFET switch 22 and the positive electrode of the load capacitor 200 maintain the same potential. Thus, the step-down circuit 244 can utilize the voltage at the switch node SW as a voltage source for powering the high voltage module 20 and step it down to a supply voltage suitable for powering the low voltage module 10 .

[0033] In some embodiments, Figure 2 As shown, the sampling and power supply module 24 may include a sampling circuit 242, which is configured to sample a sample voltage VDS at the switch node SW and output the sample voltage to the low voltage module 10. The sample voltage may indicate a voltage state at the switch node SW, and the control logic 12 of the low voltage module 10 may generate a switch signal output to the gate G of the MOSFET switch 22 based on the sample voltage. In some embodiments, the sampling circuit 242 may be configured to determine a voltage difference between the drain D and the source of the MOSFET switch 22 as the sample voltage. It should be understood that the illustrated embodiment is merely exemplary.

[0034] In some embodiments, Figure 2 As shown, the low voltage module 10 may further include a detection module 14 and a driver 16. Each module 12, 14, 16 of the low voltage module 10 may be powered by a power supply voltage VDD provided by a sampling and power supply module 24. The detection module 14 may be configured to judge the sampled voltage VDS from the sampling and power supply module 24, and as an example, the sampled voltage may be compared with a predetermined threshold voltage, and the comparison result may be output to the control logic 12, so that the control logic 12 generates a switching signal output to the gate G of the MOSFET switch 22 based on the comparison result. The driver 16 may be configured to drive the MOSFET switch 22 to turn on or off based on the switching signal from the control logic 12.

[0035] Figure 3 FIG. 2 shows a schematic diagram of an implementation of a driving circuit 100 according to a second embodiment of the present disclosure. Figure 3 The embodiment shown is Figure 2 The embodiment shown is similar, except that the detection module 14 may include multiple modules to further improve the performance of the driving circuit 100 .

[0036] In some embodiments, Figure 3 As shown, the low voltage module 10 may further include a first comparison module 142. The first comparison module 142 may be configured to compare the sampled voltage VDS with a first predetermined threshold voltage and output the comparison result to the control logic 12. The control logic 12 generates a switch signal output to the gate G of the MOSFET switch 22 based on the comparison result.

[0037] In some embodiments, Figure 3 As shown, the low voltage module 10 may further include a second comparison module 144. The second comparison module 144 may be configured to compare the supply voltage with the second predetermined threshold voltage, and generate a control logic enable signal in response to the supply voltage being greater than the second predetermined threshold voltage, the enable signal permitting the control logic 12 to operate. The enable signal provided by the second comparator module 144 ensures that the supply voltage has a sufficient magnitude to enable the low voltage module 10, especially the control logic and the driver 16 and other components to operate normally. This can improve the system stability and reliability of the drive circuit, and can be applied even in application scenarios where the MOSFET is in an extremely low on-resistance, and effectively prevent the MOSFET from burning out.

[0038] exist Figure 1 In the embodiment shown, the driving circuit 100 is arranged on the high voltage side of the secondary side. Figure 1As shown, in the case where the drive circuit 100 can be set on the high voltage side of the secondary side, the switch node SW of the drive circuit 100 is directly connected to the load capacitor. It should be understood that this is merely exemplary. In other embodiments (for illustration), the drive circuit 100 can be set on the low voltage side of the secondary side. In the case where the drive circuit 100 can be set on the low voltage side of the secondary side, the switch node SW of the drive circuit 100 can be connected to the load capacitor via the secondary winding, for example.

[0039] Figure 4 FIG. 4 is a flow chart of a method 400 for operating a power supply according to an embodiment of the present disclosure. Figure 4 As shown, at 402, the primary side T1 switch of the transformer T is turned on to charge the primary side T1 of the transformer T. At 404, the primary side T1 switch of the transformer T is turned off so that the energy of the primary side T1 of the transformer T is inductively transferred to the secondary side T2 of the transformer T. At 406, the body diode 222 of the MOSFET switch 22 is used for freewheeling to charge the load capacitor 200. At 408, the drain D voltage of the MOSFET switch 22 is collected. At 410, in response to the drain voltage being greater than a predetermined threshold voltage, a control logic enable signal is output to allow the control logic 12 of the low voltage module 10 to operate. At 412, the control logic 12 controls the MOSFET switch 22 to turn on or off based on the drain voltage.

[0040] There are many ways to implement the control logic 12 to control the gate G of the MOSFET switch 22 to be turned on or off. In some embodiments, the control logic 12 can turn on the MOSFET switch 22 in response to the drain voltage being a negative voltage to perform secondary side freewheeling voltage regulation; and turn off the MOSFET switch 22 in response to the drain voltage being a positive voltage.

[0041] According to the drive circuit disclosed in the present invention, two different voltage domain modules are provided. In the high-voltage domain, an adaptive power supply and sampling circuit module is added to the MOSFET used as a switch, which is used to bear the high voltage in the application and convert the high voltage into a low voltage to provide it to the low-voltage domain. In the process of high-low voltage conversion, the heat generated by the large voltage drop is dissipated by itself and will not be conducted to the low-voltage domain. According to the present disclosure, not only can the existence of a high-voltage interface in the drive circuit of the low-voltage domain be avoided, but also the disturbance caused by the high-voltage to low-voltage conversion process can be avoided, reducing the complexity of heat dissipation and circuit design, further reducing the area and power consumption of the entire drive circuit, improving its heat dissipation effect, and greatly improving the power density and reliability of the drive circuit.

[0042] Through the teachings given in the above description and the related drawings, many modifications and other embodiments of the present disclosure given here will be recognized by those skilled in the art of the present disclosure. Therefore, it is to be understood that the embodiments of the present disclosure are not limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included in the scope of the present disclosure. In addition, although the above description and the related drawings describe the example embodiments in the context of some example combinations of parts and / or functions, it should be appreciated that different combinations of parts and / or functions can be provided by alternative embodiments without departing from the scope of the present disclosure. In this regard, for example, other combinations of parts and / or functions that are different from those clearly described above are also expected to be within the scope of the present disclosure. Although specific terms are used here, they are only used in a general and descriptive sense and are not intended to be limited.

Claims

1. A drive circuit (100) for a power supply, the power supply comprising a transformer (T), the drive circuit (100) being arranged on a secondary side (T2) of the transformer (T), the drive circuit (100) comprising: A high voltage module (20) capable of withstanding a first voltage and a low voltage module (10) capable of withstanding a second voltage, wherein the second voltage is lower than the first voltage, The high voltage module (20) comprises: A MOSFET switch (22), wherein a drain (D) of the MOSFET switch (22) is connected to a switch node (SW); A sampling and power supply module (24) configured to sample the voltage at the switch node (SW) and to provide a supply voltage to the low voltage module (10); The low voltage module (10) comprises: a detection module (14), a driver (16) and a control logic (12). The detection module (14) comprises a first comparison module (142), wherein the first comparison module (142) is configured to compare the sampled voltage with a first predetermined threshold voltage and output the comparison result to the control logic (12); wherein the control logic (12) is configured to generate a switch signal for turning on or off the MOSFET switch (22) based on the comparison result; The driver (16) is configured to drive the MOSFET switch (22) to turn on or off based on the switching signal.

2. The drive circuit (100) according to claim 1, wherein the switch node (SW) is suitable for being connected to a load capacitor (200), and when the primary side (T1) of the transformer (T) is turned off, the inductor current at the secondary side (T2) of the transformer (T) charges the load capacitor (200) through the body diode (222) of the MOSFET switch (22).

3. The driving circuit (100) according to claim 1, wherein the sampling and power supply module (24) comprises a step-down circuit (244), the step-down circuit (244) being configured to utilize the voltage at the switch node (SW) as a voltage source for powering the high voltage module (20) and step it down to the supply voltage for powering the low voltage module (10).

4. The driving circuit (100) according to claim 3, wherein the low voltage module (10) further comprises a second comparison module (144), wherein the second comparison module (144) is configured to compare the supply voltage with a second predetermined threshold voltage, and generate a control logic enable signal in response to the supply voltage being greater than the second predetermined threshold voltage, wherein the enable signal permits the control logic (12) to operate.

5. The driving circuit (100) according to claim 1, wherein the high voltage module (20) and the low voltage module (10) use a common ground electrode (VSS).

6. The driving circuit (100) according to claim 1, wherein a source (S) of the MOSFET switch (22) is grounded.

7. The drive circuit (100) according to claim 3 or 4, wherein the sampling and power supply module (24) further comprises a sampling circuit (242), wherein the sampling circuit (242) is configured to sample the voltage at the switch node (SW) and output the sampled voltage to the low voltage module (10).

8. The drive circuit (100) of claim 7, wherein the sampling circuit (242) is configured to determine a voltage difference between a drain (D) and a source (S) of the MOSFET switch (22), and use the voltage difference as the sampled voltage.

9. The driving circuit (100) according to any one of claims 1-6 and 8, wherein the first voltage is in the range of 50V-160V, and / or the second voltage is in the range of 5-10V.

10. A power supply, comprising: Transformer (T); A drive circuit (100) according to any one of claims 1 to 9, arranged at a secondary side (T2) of the transformer (T).

11. A method for operating a power supply according to claim 10, comprising: Turning on the primary side (T1) switch of the transformer (T) to charge the primary side (T1) of the transformer (T); Turning off the switch of the primary side (T1) of the transformer (T) so that the energy of the primary side (T1) of the transformer (T) is inductively transferred to the secondary side (T2) of the transformer (T); Utilizing the body diode (222) of the MOSFET switch (22) for freewheeling to charge the load capacitor (200); collecting the drain voltage of the MOSFET switch (22); In response to the drain voltage being greater than a predetermined threshold voltage, outputting a control logic enable signal to allow the control logic (12) of the low voltage module (10) to operate; The control logic (12) controls the MOSFET switch (22) to be turned on or off based on the drain voltage.

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