A switching power supply control circuit and method and a switching power supply

Abstract

The present invention discloses a switching power supply control circuit and method and a switching power supply. The switching power supply control circuit includes a first switch and a first capacitor. One end of the first switch is connected to the gate of the upper switch tube of the power stage circuit, the other end of the first switch is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the common end of the upper switch tube and the lower tube of the power stage circuit. During the period when the upper switch tube is turned off, the first switch is disconnected to charge the first capacitor so that the voltage of the first capacitor reaches the first voltage. When the upper switch tube is turned on, the first switch is closed, and the first capacitor charges the gate capacitor of the upper switch tube, and the upper switch tube reaches the turned-on state. The first capacitor and the gate capacitor of the upper switch tube are charged by a charge pump, and the upper switch tube is in the turned-on state with low conduction loss. The present invention completes the fast conduction of the upper switch tube, and when the switching power supply control circuit is integrated in the chip, low switching loss and low conduction loss can be achieved without setting external pins.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and more particularly to a switching power supply control circuit and method and a switching power supply. Background Art

[0002] In practical applications, N-type MOS is generally used for the upper switch tube of the switching power supply, especially in high-voltage applications. When the switching power supply is integrated into the chip, in order to realize the control of the upper switch tube, the chip needs an independent pin BST, and a capacitor needs to be connected between the pin BST and the pin SW outside the chip to power the control circuit of the upper switch tube inside the chip through the capacitor, such as Figure 1 As shown, taking the buck circuit as an example, the buck circuit and the control circuit of the upper switch tube Q0 are integrated in the chip. The chip has an independent pin BST. At the same time, a capacitor C1 is connected between the pin BST and the pin SW outside the chip. The capacitor C1 is charged first, and then the capacitor C1 supplies power to the control circuit, thereby completing the control of the upper switch tube.

[0003] However, in the control method of the above-mentioned prior art, an independent pin BST needs to be set outside the chip to achieve low switching loss and low conduction loss. The function of this pin is single, which reduces the freedom of choice of chip packaging form; in addition, a capacitor is connected between the external pin BST and the pin SW of the chip. This capacitor is outside the chip and has a generally large capacity, which increases the cost. Summary of the invention

[0004] In view of this, the present invention provides a switching power supply control circuit and method and a switching power supply that can achieve low switching loss and low conduction loss without setting an external pin BST when the switching power supply is integrated in the chip, which is used to solve the technical problem in the prior art that when the switching power supply control circuit is integrated in the chip, an independent pin BST needs to be set outside the chip to achieve low switching loss and low conduction loss.

[0005] The present invention provides a switching power supply control circuit, characterized in that it includes a first switch and a first capacitor, one end of the first switch is connected to the gate of a switch tube in a power stage circuit, the other end of the first switch is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the common end of the upper switch tube and the lower switch tube in the power stage circuit. During the period when the upper switch tube is turned off, the first switch is disconnected to charge the first capacitor so that the voltage of the first capacitor reaches a first voltage. When the upper switch tube is turned on, the first switch is closed, the first capacitor charges the gate capacitor of the upper switch tube, and the upper switch tube reaches an on state. A charge pump is used to charge the first capacitor and the gate capacitor of the upper switch tube or a charge pump is used to charge the gate capacitor of the upper switch tube, and the upper switch tube is in an on state with low conduction loss.

[0006] Optionally, during the period when the upper switch tube is turned off, the first capacitor is charged using an input voltage or a charge pump.

[0007] Optionally, when the upper switch tube is turned on, before the first switch is closed, the gate capacitor of the upper switch tube is charged with the input voltage so that the upper switch tube reaches a weakly turned-on state.

[0008] Optionally, the power stage circuit is a buck circuit.

[0009] Optionally, during the period when the upper switch tube is turned off, the gate-source voltage of the upper switch tube is lower than the first threshold and greater than zero.

[0010] Optionally, the switching power supply control circuit is integrated into a chip.

[0011] The present invention also provides a switching power supply control method, wherein the switching power supply control circuit comprises a first switch and a first capacitor, wherein one end of the first switch is connected to the gate of the switch tube on the power stage circuit, the other end of the first switch is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the common end of the upper switch tube and the lower tube of the power stage circuit, and the method comprises the following steps:

[0012] During the period when the upper switch tube is turned off, the first switch is turned off to charge the first capacitor so that the voltage of the first capacitor reaches the first voltage;

[0013] When the upper switch tube is turned on, the first switch is closed, the first capacitor charges the gate capacitor of the upper switch tube, and the upper switch tube reaches an on state;

[0014] The first capacitor and the gate capacitor of the upper switch tube are charged by a charge pump or the gate capacitor of the upper switch tube is charged by a charge pump, and the upper switch tube is in an on state with low conduction loss.

[0015] Optionally, during the period when the upper switch tube is turned off, the first capacitor is charged using an input voltage or a charge pump.

[0016] Optionally, when the upper switch tube is turned on, before the first switch is closed, the gate capacitor of the upper switch tube is charged with the input voltage so that the upper switch tube reaches a weakly turned-on state.

[0017] Optionally, during the period when the upper switch tube is turned off, the gate-source voltage of the upper switch tube is lower than the first threshold and greater than zero.

[0018] The present invention further proposes a switching power supply, comprising the switching power supply control circuit and the power stage circuit described above, wherein the upper switch tube of the power stage circuit is an N-type MOS tube.

[0019] The present invention has the following advantages compared with the prior art: the present invention provides a switching power supply control circuit and method, during the period when the upper switch tube is turned off, the first capacitor is charged, and when the upper switch tube is turned on, the first switch is first closed to short-circuit the first capacitor and the gate capacitor of the upper switch tube, and the first capacitor charges the gate capacitor of the upper switch tube, and the gate voltage of the upper switch tube immediately increases, and the upper switch tube quickly reaches the turned-on state, and then the first capacitor and the gate capacitor of the upper switch tube are charged by a charge pump or the gate capacitor of the upper switch tube is charged by a charge pump, so that the gate voltage of the upper switch tube is maintained at a high level, and the upper switch tube is in a turned-on state with low conduction loss. The present invention can complete the rapid conduction of the upper switch tube, and when the switching power supply control circuit is integrated in the chip, low switching loss and low conduction loss can be achieved without setting an external pin BST. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of a switching power supply control circuit in the prior art;

[0021] Figure 2 It is a schematic structural diagram of an embodiment of a switching power supply control circuit of the present invention. DETAILED DESCRIPTION

[0022] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitution, modification, equivalent method and scheme made within the spirit and scope of the present invention.

[0023] In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without these detailed descriptions.

[0024] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the accompanying drawings are all simplified and not in exact proportion, and are only used for the purpose of conveniently and clearly assisting in explaining the embodiments of the present invention.

[0025] The switching power supply control circuit of the present invention comprises a first switch and a first capacitor, one end of the first switch is connected to the gate of the upper switch tube of the power stage circuit, the other end of the first switch is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the common end of the upper switch tube and the lower switch tube of the power stage circuit. During the period when the upper switch tube is turned off, the first switch is disconnected to charge the first capacitor so that the voltage of the first capacitor reaches the first voltage. When the upper switch tube is turned on, the first switch is closed, the first capacitor charges the gate capacitor of the upper switch tube, and the upper switch tube reaches the turned-on state. The charge pump is used to charge the first capacitor and the gate capacitor of the upper switch tube or the charge pump is used to charge the gate capacitor of the upper switch tube, and the upper switch tube is in the turned-on state with low conduction loss. The upper switch tube is a switch tube with one end connected to the high potential end of the input voltage, and the lower tube refers to a switch tube or a diode with one end connected to the low potential end of the input voltage.

[0026] During the period when the upper switch tube of the switching power supply is turned off, the first capacitor is pre-charged to a higher level by using a charge pump or an input voltage; when the upper switch tube is turned on, the first switch is closed, the first capacitor and the gate capacitor of the upper switch tube are short-circuited, and due to the charge transfer, the gate voltage of the upper switch tube will immediately increase, so that the upper switch tube quickly reaches a better turn-on state; then the first capacitor and the gate capacitor of the upper switch tube are further charged by the charge pump, or only the gate capacitor of the upper switch tube is charged by the charge pump, so that the gate voltage of the upper switch tube continues to increase or remains at a higher level, ensuring that the upper switch tube is in a good turn-on state and maintaining a small on-resistance.

[0027] When the upper switch tube is turned off, the gate-source voltage of the upper switch tube is lower than the first threshold and greater than zero. When the upper switch tube is turned on, there is already a voltage greater than zero and lower than the first threshold on the gate capacitor of the upper switch tube, which will make the upper switch tube turn on faster.

[0028] The above-mentioned switching power supply control circuit is applied to a power stage circuit in which the upper switch tube is an N-type MOS tube.

[0029] In addition, when the power stage circuit is a buck circuit, when the upper switch tube is turned on, before closing the first switch, the gate capacitor of the upper switch tube is first charged with the input voltage so that the upper switch tube reaches a weakly turned-on state, which can also make the turning-on speed of the upper switch tube faster.

[0030] There are many embodiments of the switching power supply control circuit. Figure 1 An embodiment is given. Figure 1As shown, the power stage circuit is a buck circuit, including a switch tube Q0, a lower tube Q1, and an inductor L0. The drain of the switch tube Q0 is connected to the high potential end of the input voltage, the gate of the switch tube Q0 is connected to the gate of the drive control circuit, the source of the switch tube Q0 is connected to the negative electrode of the lower tube, the positive electrode of the lower tube is connected to the low potential end of the input voltage, one end of the inductor L0 is connected to the common end of the switch tube Q0 and the lower tube Q1, the other end of the inductor L0 is connected to one end of the resistor R0, the other end of the resistor R0 is connected to the low potential end of the input voltage, and the capacitor C0 and the resistor R0 are connected in parallel.

[0031] The switching power supply control circuit includes a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch tube S5, a charge pump and a first capacitor C1. One end of the first switch S1 is connected to the gate of the switch tube Q0 on the power stage circuit, the other end of the first switch S1 is connected to one end of the first capacitor C1, the other end of the first capacitor C1 is connected to the common end of the switch tube Q0 on the power stage circuit and the lower tube Q1, one end of the second switch S2 is connected to the gate of the upper switch tube Q0 via a diode D1, the other end of the second switch S2 receives an input voltage Vin, one end of the third switch S3 is connected to the common end of the first capacitor C1 and the first switch S1, the other end of the third switch receives the input voltage Vin, one end of the fourth switch S4 is connected to the common end of the first capacitor C1 and the first switch S1, the other end of the fourth switch tube is connected to the charge pump, one end of the fifth switch S5 is connected to the gate of the upper switch tube Q0, and the other end is connected to the charge pump, and the input of the charge pump is the input voltage.

[0032] The specific control process of the above embodiment is as follows:

[0033] 1: When the upper switch tube Q0 is turned off, the fourth switch S4 is closed to use the charge pump to precharge the first capacitor C1 to the first voltage. The first voltage is a relatively high level. When the input voltage VIN is low or the voltage difference between VIN and VOUT is small (DCM), the charge pump can use multiple stages to reduce the demand for the capacitance value of the first capacitor C1;

[0034] When the upper switch tube Q0 needs to be turned on, the fourth switch S4 is turned off, the second switch S2 is turned on, and the input voltage VIN charges the gate capacitor Cg of the upper switch tube, so that the upper switch tube Q0 is in a weakly turned-on state, and SW starts to rise;

[0035] When the first switch S1 is closed, the first capacitor C1 charges the upper switch gate capacitor Cg. The charge of the first capacitor C1 will be transferred to the upper switch gate capacitor Cg, so that the gate voltage of the upper switch tube increases immediately, and SW can quickly rise to the VIN level to reduce switching loss;

[0036] The fourth switch S4 is closed, and the charge pump continues to charge C1 and Cg (or the fifth switch S5 is closed, and the charge pump continues to charge Cg), so that the gate voltage of the upper switch tube further rises or remains at a high level, thereby ensuring that the upper switch tube is in a low on-impedance state and reducing conduction loss.

[0037] 2: For applications where the input voltage VIN is high (CCM) or the input voltage VIN is high and the output voltage VOUT is low (DCM), during the period when the upper switch is turned off, the charge pump can be turned off to save power consumption, and the third switch S3 is closed to use the input voltage Vin to pre-charge the first capacitor C1 to the input voltage VIN level;

[0038] When the upper switch tube Q0 needs to be turned on, the third switch S3 is turned off, the second switch S2 is turned on, and the input voltage VIN charges the gate capacitor Cg of the upper switch tube, so that the upper switch tube Q0 is in a weakly turned-on state, and SW starts to rise;

[0039] When the first switch S1 is closed, the first capacitor C1 charges the upper switch gate capacitor Cg. The charge of the first capacitor C1 will be transferred to the upper switch gate capacitor Cg, so that the gate voltage of the upper switch tube increases immediately, and SW can quickly rise to the VIN level to reduce switching loss;

[0040] The fourth switch S4 is closed, and the charge pump continues to charge C1 and Cg (or the fifth switch S5 is closed, and the charge pump continues to charge Cg), so that the gate voltage of the upper switch tube further rises or remains at a high level, thereby ensuring that the upper switch tube is in a low on-impedance state and reducing conduction loss.

[0041] Therefore, the above embodiment is a better solution, and the energy consumption and fast start-up requirements are taken into consideration when choosing to charge the first capacitor C1 using the input voltage or the charge pump. In other embodiments, the first capacitor C1 can be charged using only the charge pump, and in other embodiments, the first capacitor is charged using only the input voltage, all of which are within the protection scope of the present invention.

[0042] In some embodiments, the step of charging the gate capacitor Cg of the upper switch tube by the input voltage is not performed, which may slow down the turn-on speed, but it is also within the protection scope of the present invention. In some embodiments, during the period when the upper switch tube is turned off, the gate-source voltage of the upper switch tube is lower than the first threshold value and greater than zero, which can achieve the same effect as charging the gate capacitor Cg of the upper switch tube by the input voltage, which is also within the protection scope of the present invention.

[0043] In the boost circuit, when turning on the upper switch, there is no need to open the connection between the input voltage and the gate of the upper switch, because the inductor current will cause SW to directly increase to a point higher than the input voltage by the forward voltage drop of the upper switch body diode, and the upper switch gate capacitance cannot be charged by the input voltage; therefore, in the boost circuit, except for omitting the step of opening the connection between the input voltage and the gate of the upper switch, the rest is the same as the buck circuit.

[0044] Since there is no input voltage to charge the gate capacitance of the upper switch, the switch on the boost circuit will be slower than the buck circuit. But this can be improved in the control process. During the shutdown of the upper switch, the gate-source voltage of the upper switch is lower than the first threshold and greater than zero. The first threshold is less than the voltage drop Vth when the main switch is turned on. At this time, it is equivalent to the voltage pre-stored in the gate capacitance Cg of the upper switch. When the upper switch needs to be turned on, the first capacitor C1 will charge the gate capacitance Cg of the upper switch more quickly, so that the upper switch can be turned on more quickly.

[0045] When the switching power supply control circuit is integrated into the chip, the upper switch tube can be quickly turned on without setting the external pin BST.

[0046] Although the embodiments are described and illustrated separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments can be replaced and integrated. If the content is not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0047] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. A switching power supply control circuit, characterized in that: It includes a first switch and a first capacitor, one end of the first switch is connected to the gate of the switch tube on the power stage circuit, the other end of the first switch is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the common end of the switch tube on the power stage circuit and the lower tube, During the off period of the upper switch tube, the first switch is turned off, and the first capacitor is charged by the input voltage or the charge pump so that the voltage of the first capacitor reaches the first voltage. When the upper switch tube is turned on, the first switch is closed, the first capacitor charges the gate capacitor of the upper switch tube, and the upper switch tube reaches the turned-on state, the fourth switch is closed, the charge pump is used to charge the first capacitor and the gate capacitor of the upper switch tube or the charge pump is used to charge the gate capacitor of the upper switch tube, and the upper switch tube is in the turned-on state with low conduction loss, wherein the fourth switch is connected between the charge pump and one end of the first capacitor, The switching power supply control circuit is integrated in the chip.

2. The switching power supply control circuit according to claim 1, characterized in that: When the upper switch tube is turned on, before the first switch is closed, the gate capacitance of the upper switch tube is charged by the input voltage.

3. The switching power supply control circuit according to claim 2, characterized in that: The power stage circuit is a buck circuit.

4. The switching power supply control circuit according to claim 1, characterized in that: During the period when the upper switch tube is turned off, the gate-source voltage of the upper switch tube is lower than the first threshold and greater than zero.

5. A switching power supply control method, applied to a switching power supply control circuit, wherein the switching power supply control circuit comprises a first switch and a first capacitor, wherein one end of the first switch is connected to a gate of a switch tube on a power stage circuit, the other end of the first switch is connected to one end of a first capacitor, and the other end of the first capacitor is connected to a common end of an upper switch tube and a lower tube in the power stage circuit, characterized in that: The following steps are involved: During the period when the upper switch tube is turned off, the first switch is turned off, and the first capacitor is charged by using the input voltage or the charge pump so that the voltage of the first capacitor reaches the first voltage; When the upper switch tube is turned on, the first switch is closed, the first capacitor charges the gate capacitor of the upper switch tube, and the upper switch tube reaches an on state; The first capacitor and the gate capacitor of the upper switch tube are charged by a charge pump or the gate capacitor of the upper switch tube is charged by a charge pump, and the upper switch tube is in an on state with low conduction loss. The switching power supply control circuit is integrated in the chip.

6. The switching power supply control method according to claim 5, characterized in that: During the off period of the upper switch tube, the first capacitor is charged by using the input voltage or a charge pump.

7. The switching power supply control method according to claim 5 or 6, characterized in that: When the upper switch tube is turned on, before the first switch is closed, the gate capacitance of the upper switch tube is charged by the input voltage.

8. The switching power supply control method according to claim 5 or 6, characterized in that: During the period when the upper switch tube is turned off, the gate-source voltage of the upper switch tube is lower than the first threshold and greater than zero.

9. A switching power supply, comprising the switching power supply control circuit and a power stage circuit according to claim 1, wherein the upper switch tube of the power stage circuit is an N-type MOS tube.

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