Driving circuit and DC-DC switching power supply

Abstract

The utility model discloses a kind of driving circuit and DC-DC switching power supply, switching power supply includes power tube, the first end of power tube is connected with reference voltage, the second end of power tube is connected with the switching node of switching power supply, driving circuit includes: voltage division control unit, conversion unit and comparison driving unit, voltage division control unit generates first comparison voltage when power tube opens based on the current flowing into switching node;Conversion unit generates second comparison voltage based on feedback current;Comparison driving unit exports driving signal for controlling power tube based on first comparison voltage and second comparison voltage.The driving circuit according to the utility model, by optimizing circuit design, ensure that even larger inductance current value, under low input voltage, driving circuit still can work normally, and high voltage tube used for sampling is reduced by half, greatly reduce the area of chip.

Description

Technical Field

[0001] This utility model belongs to the field of integrated circuit technology, specifically relating to a driving circuit and a DC-DC switching power supply. Background Technology

[0002] Under varying input voltages and output loads, DC-DC switching power supplies require closed-loop control and negative feedback to maintain stable output voltage. Peak current control is a commonly used closed-loop control method, typically involving a sampling circuit (RCS) connected in series at the source of the power transistor to detect the inductor current and achieve closed-loop regulation and overcurrent protection. In DC-DC switching power supplies, the built-in power transistor is an nLDMOS (N-channel lateral double-diffused metal-oxide-semiconductor field-effect transistor, also known as a high-voltage transistor) to meet voltage withstand requirements, utilizing its on-resistance R... DSON It is used as a sampling resistor to detect inductor current.

[0003] For example Figure 1 Taking the BOOST converter shown as an example, the error amplifier amplifies the error information between the voltage of the feedback node FB and the internal reference voltage and converts it into a feedback current ICON. The feedback current ICON acts on the resistor R inside the current sampling and comparison circuit. SENSE When the voltage is converted to voltage and the power transistor is turned on, the current in the inductor L increases linearly, and the voltage at the switching node SW increases linearly. When the voltage at the switching node SW is higher than that at the resistor R... SENSE The power transistor is turned off after the voltage drop across it. However, in order to obtain a relatively large inductor current peak I... PEAK When the input voltage VIN is relatively low (e.g., 2.5V), the existing current sampling and comparison circuit will not work properly, and the use of a large number of nLDMOS transistors will also occupy a large area of ​​the chip.

[0004] Figure 2 This is an existing current sampling and comparison circuit used in DC-DC switching power supplies, where MN1~MN2n-1 are all nLDMOS transistors. The gates of MNn+1~MN2n-1 are connected to the power supply voltage VCC and are always in the on-state. When the voltage at node GATE is high, MN1~MNn are turned on. The on-resistance of power transistor MN1 is R. DSON The on-resistance of this series of nLDMOS transistors MN2~MNn is R. SENSE The dimensions of MNn+1 to MN2n-1 are the same as those of MN2 to MNn, and their on-resistance is also R. SENSE The current source I1 = I2. After the voltage at node GATE is high, the voltage V at switch node SW... SW =I PEAK ×R DSON , where I PEAKThis refers to the peak current on the inductor L on the chip's peripheral topology. Near the comparator CMP switching threshold, the voltage Va at node a = I1 × R. SENSE +I PEAK ×R DSON The voltage V at the node into which current ICON flows. ICON =(I²+ICON)×R SENSE Near the flip threshold, Va = V ICON Since I1 = I2, therefore I PEAK ×R DSON = ICON× R SENSE Therefore, we can obtain I. PEAK = ICON× R SENSE / R DSON R of a typical power transistor DSON It will be determined at the beginning, so to obtain a relatively large I PEAK This necessitates increasing the ICON size or the number of nLDMOS transistors connected in series to increase R. SENSE However, with a lower input voltage (2.5V), the supply voltage VCC is also 2.5V. A larger ICON or more nLDMOS transistors in series will cause MNn+1 to operate in the saturation region, thus leading to V... ICON At a relatively high voltage, the comparator CMP cannot flip, and the increase in the number of nLDMOS transistors further increases the chip area.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of this utility model and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Utility Model Content

[0006] The purpose of this invention is to provide a driving circuit and a DC-DC switching power supply that can still operate normally even under low input voltage, and to reduce the chip area by reducing the number of nLDMOS transistors in the sampling circuit.

[0007] To achieve the above objectives, a specific embodiment of this utility model provides the following technical solution: a driving circuit for a switching power supply, the switching power supply including a power transistor, a first terminal of the power transistor being connected to a reference voltage, and a second terminal of the power transistor being connected to a switching node of the switching power supply; the driving circuit includes:

[0008] The voltage divider control unit is connected to the first input terminal of the switching node and the comparator drive unit to generate a first comparison voltage based on the current flowing into the switching node when the power transistor is turned on.

[0009] A conversion unit, connected to the second input terminal of the comparison drive unit, simultaneously receives feedback current from the switching power supply to generate a second comparison voltage based on the feedback current; and

[0010] The comparator drive unit is connected to the control terminal of the power transistor. The comparator drive unit outputs a drive signal for controlling the power transistor based on a first comparison voltage and a second comparison voltage.

[0011] In one or more embodiments of this utility model, the voltage divider control unit includes a voltage divider module and a switch module. The voltage divider module is connected to the switch module, the switch node, and the first input terminal of the comparison drive unit. The switch module is connected to the output terminal of the comparison drive unit. The switch module controls the on / off connection between the voltage divider module and the switch node based on the drive signal.

[0012] In one or more embodiments of this utility model, the voltage divider module includes a first voltage divider resistor and a second voltage divider resistor. The first end of the second voltage divider resistor is connected to the first input terminal of the comparator drive unit, and the second end of the second voltage divider resistor is connected to the reference voltage. The first voltage divider resistor is connected in series with the switching module and is connected to the switching node and the first end of the second voltage divider resistor.

[0013] In one or more embodiments of this utility model, the switching module includes a switching transistor, the control terminal of which is used to receive a drive signal, and the switching transistor is connected to the branch where the switching node and the voltage divider module are located to control the on / off state of the branch based on the drive signal.

[0014] In one or more embodiments of this utility model, the switching transistor is a high-voltage resistant transistor.

[0015] In one or more embodiments of the present invention, the conversion unit includes one or more transistors, the control terminal of the transistors is used to receive a bias voltage, and the one or more transistors are connected in series between the second input terminal of the comparator driving unit and the reference voltage, and simultaneously receive feedback current.

[0016] In one or more embodiments of this utility model, the transistor is a high-voltage resistant transistor.

[0017] In one or more embodiments of this utility model, the comparison drive unit includes a comparator and a PWM controller. The first input terminal of the comparator is connected to a voltage divider control unit to receive a first comparison voltage. The second input terminal of the comparator is connected to a conversion unit to receive a second comparison voltage. The output terminal of the comparator is connected to the input terminal of the PWM controller. The output terminal of the PWM controller is connected to the control terminal of the power transistor. The PWM controller is used to generate a drive signal based on the comparison signal generated by the comparator.

[0018] This utility model also discloses a DC-DC switching power supply, including: a power transistor and the aforementioned driving circuit, wherein the control terminal of the power transistor is connected to the output terminal of the comparator driving unit, the first terminal of the power transistor is connected to a reference voltage, and the second terminal of the power transistor is connected to the switching node of the DC-DC switching power supply.

[0019] In one or more embodiments of this utility model, the DC-DC switching power supply further includes an inductor, a diode, a feedback unit, an error amplifier, and a voltage-to-current circuit. The first end of the inductor is used to receive the input voltage, and the second end of the inductor is connected to the second end of the power transistor and the anode of the diode to form a switching node. The feedback unit is connected to the cathode of the diode and generates a feedback voltage based on the output voltage of the DC-DC switching power supply. The error amplifier is used to amplify the error between the feedback voltage and the reference voltage to generate an error signal. The voltage-to-current circuit is used to convert the error signal into a feedback current.

[0020] Compared with the prior art, the driving circuit and DC-DC switching power supply of this utility model, through optimized circuit design, ensure that the driving circuit can still work normally even under low input voltage while obtaining a relatively large inductor current value. Furthermore, the high-voltage transistor used for sampling is reduced by almost half, greatly reducing the chip area. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a DC-DC switching power supply in the prior art.

[0023] Figure 2 This is a circuit diagram of a driving circuit in the prior art.

[0024] Figure 3 This is a circuit diagram of the driving circuit in one embodiment of the present invention.

[0025] Figure 4 This is a circuit diagram of a DC-DC switching power supply according to one embodiment of the present invention. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0027] The terms "coupled," "connected," or "linked" in this specification include both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as an electrical conduction medium, which may have parasitic inductance or capacitance. Indirect connections may also include connections made through other active or passive devices to achieve the same or similar functional purpose, such as connections through switches, follower circuits, or other circuits or components. Furthermore, in utility models, terms such as "first" and "second" are primarily used to distinguish one technical feature from another, and do not necessarily require or imply any actual relationship, quantity, or order between these technical features.

[0028] In the detailed description of this specification, reference is made to the accompanying drawings, which form a part thereof, wherein like reference numerals always denote like parts, and wherein exemplary embodiments are shown by way of example that may be implemented. It should be understood that other embodiments may be utilized, and structural or logical changes may be made, without departing from the scope of this disclosure. Therefore, the following detailed description should not be considered limiting.

[0029] The various operations in the specification may be described sequentially as multiple discrete actions or operations in a manner most conducive to understanding the claimed subject matter. However, the order of description should not be construed as implying that these operations must be sequentially related. Specifically, these operations may not be performed in the order presented. The described operations may be performed in a different order than in the described embodiments. Various additional operations may be performed in additional embodiments and / or the described operations may be omitted.

[0030] For the purposes of this disclosure, the phrase “A and / or B” means (A), (B), or (A and B). For the purposes of this disclosure, the phrase “A, B and / or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).

[0031] Various components and devices may be referred to or shown in the singular (e.g., “transistor”, “transistor”, “switch”, etc.) in this document, but only for the convenience of discussion, and any element referred to in the singular may include multiple such elements as taught herein.

[0032] The description uses the phrases "in one embodiment," "in other embodiments," or "in some embodiments," each of which may refer to one or more of the same or different embodiments. Furthermore, the terms "comprising," "including," "having," etc., used with respect to embodiments of this disclosure are synonymous.

[0033] like Figure 3 As shown, a driving circuit in one embodiment of the present invention is used for a switching power supply. The switching power supply includes a power transistor MN1. The first terminal of the power transistor MN1 is connected to a reference voltage, and the second terminal of the power transistor MN1 is connected to the switching node SW of the switching power supply. In one embodiment, the reference voltage is ground voltage.

[0034] like Figure 3 As shown, the driving circuit includes: a voltage divider control unit 10, a conversion unit 20, and a comparison driving unit 30.

[0035] The voltage divider control unit 10 is connected to the switching node SW and the first input terminal of the comparator drive unit 30 to generate a first comparison voltage V1 based on the current flowing into the switching node SW when the power transistor MN1 is turned on. The conversion unit 20 is connected to the second input terminal of the comparator drive unit 30, and the conversion unit 20 also receives the feedback current ICON from the output terminal of the switching power supply to generate a second comparison voltage V2 based on the feedback current ICON.

[0036] The comparison drive unit 30 is connected to the control terminal of the power transistor MN1. The comparison drive unit 30 outputs a drive signal VK for controlling the power transistor MN1 based on the first comparison voltage V1 and the second comparison voltage V2.

[0037] In one embodiment, the voltage divider control unit 10 includes a voltage divider module and a switch module. The voltage divider module is connected to the switch module, the switch node SW, and the first input terminal of the comparison drive unit 30. The switch module is connected to the output terminal of the comparison drive unit 30. The switch module controls the on / off connection between the voltage divider module and the switch node SW based on the drive signal VK.

[0038] The voltage divider module includes a first voltage divider resistor Rp1 and a second voltage divider resistor Rp2. The first end of the second voltage divider resistor Rp2 is connected to the first input terminal of the comparator drive unit 30, and the second end of the second voltage divider resistor Rp2 is connected to the reference voltage. The first voltage divider resistor Rp1 is connected in series with the switch module and is connected to the switch node SW and the first end of the second voltage divider resistor Rp2.

[0039] The switching module includes a switching transistor MK. The control terminal of the switching transistor MK receives a drive signal VK. The switching transistor MK is connected to the branch containing the switching node SW and the voltage divider module to control the on / off state of the branch based on the drive signal VK. Specifically, the first terminal of the switching transistor MK is connected to the first terminal of the second voltage divider resistor Rp2 and the first input terminal of the comparator drive unit 30. The second terminal of the switching transistor MK is connected to the first terminal of the first voltage divider resistor Rp1. The second terminal of the first voltage divider resistor Rp1 is connected to the switching node SW. The control terminal of the switching transistor MK receives the drive signal VK. In one embodiment, the switching transistor MK is a high-voltage resistant transistor.

[0040] The conversion unit 20 includes one or more transistors Ma1, Ma2...Man. The control terminal of each transistor is used to receive a bias voltage. In one embodiment, the bias voltage is the power supply voltage VCC. One or more transistors are connected in series between the second input terminal of the comparator drive unit 30 and the reference voltage, and simultaneously receive the feedback current ICON. In one embodiment, transistors Ma1, Ma2...Man are high-voltage transistors (i.e., nLDMOS transistors), and the number of transistors can be selected as needed.

[0041] The comparison drive unit 30 includes a comparator CMP and a PWM controller. The first input terminal of the comparator CMP is connected to the voltage divider control unit 10 to receive a first comparison voltage V1. The second input terminal of the comparator CMP is connected to the conversion unit 20 to receive a second comparison voltage V2. The output terminal of the comparator CMP is connected to the input terminal of the PWM controller. The output terminal of the PWM controller is connected to the control terminal of the power transistor MN1. The PWM controller is used to generate a drive signal VK based on the comparison signal generated by the comparator CMP.

[0042] like Figure 4 As shown, this utility model also discloses a DC-DC switching power supply, including: a power transistor MN1 and a driving circuit. The control terminal of the power transistor MN1 is connected to the output terminal of the PWM controller of the comparator driving unit 30. The first terminal of the power transistor MN1 is connected to the reference voltage, and the second terminal of the power transistor MN1 is connected to the switching node SW of the DC-DC switching power supply.

[0043] The DC-DC switching power supply also includes an inductor L, a diode D, a feedback unit, an error amplifier, and a voltage-to-current converter. The first terminal of inductor L receives the input voltage VIN, and the second terminal of inductor L is connected to the second terminal of power transistor MN1 and the anode of diode D to form a switching node SW. The feedback unit is connected to the cathode of diode D and generates a feedback voltage based on the output voltage VOUT of the DC-DC switching power supply. The feedback unit includes resistors Ra and Rb, which are connected in series to divide the output voltage VOUT to generate the feedback voltage, which is then sent to the feedback node FB. The error amplifier amplifies the error between the feedback voltage and the reference voltage to generate an error signal, and the voltage-to-current converter converts the error signal into a feedback current ICON.

[0044] Under normal operating conditions of the drive circuit, Ma1, Ma2~Man are always in the conducting state. After the drive signal VK is high, the power transistor MN1 is turned on, and the switching transistor MK is also turned on and operates in the linear region. The voltage of the switching node SW increases linearly.

[0045] When V1=I is near the toggle threshold of comparator CMP PEAK ×R DSON ×Rp2 / (Rp1+Rp2+R MK ), I PEAK R is the peak current through inductor L. DSON R is the on-resistance of power transistor MN1. MK V2 is the on-resistance of the switching transistor MK, where V2 = ICON × R SENSE R SENSE Let V1 be the sum of the on-resistances of transistors Ma1, Ma2...Man, and let V1 = V2, thus I... PEAK = ICON× R SENSE ×(Rp1+Rp2+R MK ) / (R DSON ×Rp2). In order to obtain a relatively large I PEAK Simply adjust the ratio of the first voltage divider resistor Rp1 and the second voltage divider resistor Rp2.

[0046] Even at low input voltage VIN, transistors Ma1, Ma2...Man all operate in the linear region, and the circuit functions normally. Furthermore, compared to... Figure 2 The original scheme shown uses 2n-1 nLDMOS transistors. Figure 3 The proposed solution only requires n nLDMOS transistors, which greatly reduces the chip area.

[0047] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0048] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A driving circuit, characterized in that, A switching power supply, the switching power supply including a power transistor, a first terminal of the power transistor being connected to a reference voltage, and a second terminal of the power transistor being connected to a switching node of the switching power supply, the driving circuit including: The voltage divider control unit is connected to the first input terminal of the switching node and the comparator drive unit to generate a first comparison voltage based on the current flowing into the switching node when the power transistor is turned on. A conversion unit, connected to the second input terminal of the comparison drive unit, simultaneously receives feedback current from the switching power supply to generate a second comparison voltage based on the feedback current; and The comparator drive unit is connected to the control terminal of the power transistor. The comparator drive unit outputs a drive signal for controlling the power transistor based on a first comparison voltage and a second comparison voltage.

2. The driving circuit according to claim 1, characterized in that, The voltage divider control unit includes a voltage divider module and a switch module. The voltage divider module is connected to the switch module, the switch node, and the first input terminal of the comparison drive unit. The switch module is connected to the output terminal of the comparison drive unit. The switch module controls the on / off connection between the voltage divider module and the switch node based on the drive signal.

3. The driving circuit according to claim 2, characterized in that, The voltage divider module includes a first voltage divider resistor and a second voltage divider resistor. The first end of the second voltage divider resistor is connected to the first input terminal of the comparator drive unit, and the second end of the second voltage divider resistor is connected to the reference voltage. The first voltage divider resistor is connected in series with the switching module and is connected to the switching node and the first end of the second voltage divider resistor.

4. The driving circuit according to claim 2, characterized in that, The switching module includes a switching transistor. The control terminal of the switching transistor is used to receive a drive signal. The switching transistor is connected to the branch where the switching node and the voltage divider module are located to control the on / off state of the branch based on the drive signal.

5. The driving circuit according to claim 4, characterized in that, The switching transistor is a high-voltage resistant transistor.

6. The driving circuit according to claim 1, characterized in that, The conversion unit includes one or more transistors, the control terminal of which is used to receive a bias voltage, and the one or more transistors are connected in series between the second input terminal of the comparator drive unit and the reference voltage, and simultaneously receive feedback current.

7. The driving circuit according to claim 6, characterized in that, The transistor is a high-voltage resistant transistor.

8. The driving circuit according to claim 1, characterized in that, The comparison drive unit includes a comparator and a PWM controller. The first input terminal of the comparator is connected to a voltage divider control unit to receive a first comparison voltage. The second input terminal of the comparator is connected to a conversion unit to receive a second comparison voltage. The output terminal of the comparator is connected to the input terminal of the PWM controller. The output terminal of the PWM controller is connected to the control terminal of the power transistor. The PWM controller is used to generate a drive signal based on the comparison signal generated by the comparator.

9. A DC-DC switching power supply, characterized in that, include: The power transistor and the driving circuit as described in any one of claims 1 to 8, wherein the control terminal of the power transistor is connected to the output terminal of the comparator driving unit, the first terminal of the power transistor is connected to the reference voltage, and the second terminal of the power transistor is connected to the switching node of the DC-DC switching power supply.

10. The DC-DC switching power supply according to claim 9, characterized in that, The DC-DC switching power supply also includes an inductor, a diode, a feedback unit, an error amplifier, and a voltage-to-current circuit. The first end of the inductor is used to receive the input voltage, and the second end of the inductor is connected to the second end of the power transistor and the anode of the diode to form a switching node. The feedback unit is connected to the cathode of the diode and generates a feedback voltage based on the output voltage of the DC-DC switching power supply. The error amplifier is used to amplify the error between the feedback voltage and the reference voltage to generate an error signal. The voltage-to-current circuit is used to convert the error signal into a feedback current.

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