A redundant circuit and a switching converter applying the same

Abstract

The application provides a redundant circuit and a switching converter using the same. The redundant circuit comprises a power tube and a driving circuit of the power tube. The first end of the power tube receives an input voltage, and the second end of the power tube is connected to a load to generate an output voltage. The driving circuit comprises a first current generator configured to generate a first current according to the difference between the input voltage and the output voltage; a pull-up current generator configured to generate a pull-up current according to the difference between a second preset current and the first current; and a pull-down current generator configured to generate a pull-down current according to the first current and the pull-up current. The difference between the pull-up current and the pull-down current is used to drive the power tube. When the load is empty, the difference between the second preset current and the first current is less than or equal to zero, so that the pull-up current and the pull-down current are both zero. The application can optimize the static power consumption when the load is empty.

Description

Technical Field

[0001] This invention relates to the field of power electronics, and in particular to a redundant circuit and a switching converter using the same. Background Technology

[0002] In circuit systems, redundant circuits are often introduced to improve system stability and reliability. For example, in a switching power supply system, redundant circuits are introduced at the output of the switching power supply to prevent current from flowing back to the input.

[0003] See Figure 1 The diagram illustrates a redundant circuit, including a power transistor M1 and its driving circuit. The first terminal of the power transistor M1 receives an input voltage VIN, and its second terminal is connected to a load with a load voltage VOUT. In the prior art, the driving circuit provides a pull-up current to charge the gate capacitance of the power transistor M1 to drive the power transistor M1 to turn on. When the load is lightly loaded, the gate voltage of the power transistor M1 is adjusted through the loop to control the voltage difference between VIN and VOUT within a certain range. When the loop is stable, the pull-down current of the power transistor M1 is equal to the pull-up current. When the load is unloaded, the gate voltage of the power transistor M1 is adjusted to the body / source voltage of the power transistor to turn off the power transistor, but the pull-up current still exists, which will bring certain losses.

[0004] The pull-up current of the power transistor gate and the static power consumption of the power transistor are mutually constrained. If the pull-up current is designed to be large, the pull-up current will still exist when the load is unloaded, which will increase the static power consumption of the power transistor accordingly. Summary of the Invention

[0005] The purpose of this invention is to provide a redundant circuit and a switching converter using the same, in which the power transistor of the redundant circuit can be turned on quickly when the load is heavy or during startup, and no drive current is consumed when the load is light, thereby optimizing static power consumption.

[0006] This invention proposes a redundant circuit, including a power transistor and its driving circuit. The first terminal of the power transistor receives an input voltage, and its second terminal is connected to a load to generate an output voltage. The driving circuit includes:

[0007] The first current generating unit generates a first current based on the difference between the input voltage and the output voltage and a first preset current;

[0008] The pull-up current generating unit generates a pull-up current based on the difference between the second preset current and the first current;

[0009] A pull-down current generating unit generates a pull-down current based on the first current and the pull-up current;

[0010] The difference between the pull-up current and the pull-down current is used to drive the power transistor.

[0011] When the load is unloaded, the difference between the second preset current and the first current is less than or equal to zero, so that both the pull-up current and the pull-down current are zero.

[0012] Optionally, the first current is proportional to the first preset current.

[0013] Optionally, when the load is greater than the heavy load reference, the pull-up current is proportional to the first preset current.

[0014] Optionally, the first current and the pull-down current are both zero.

[0015] Optionally, when the load is less than the heavy load reference and the load is not unloaded, when the redundant circuit enters a steady state, the pull-up current is equal to the pull-down current and equal to the preset current.

[0016] Optionally, the difference between the input voltage and the output voltage is a preset voltage difference.

[0017] Optionally, when the load is less than the heavy load reference, the first current is equal to K1×(VOUT-VIN)+K2×Is1, where VOUT is the output voltage, VIN is the input voltage, Is1 is the first preset current, and K1 and K2 are preset constants greater than zero.

[0018] Optionally, when the load is not unloaded, the pull-up current is K3×(Is2-I1), where Is2 is the second preset current, I1 is the first current, and K3 is a constant greater than zero.

[0019] Optionally, the first current generating unit includes an operational amplifier, a first constant current source, a first transistor, and a second transistor, wherein the first constant current source outputs the first preset current;

[0020] The first input terminal of the operational amplifier receives the output voltage through a first resistor, and the second input terminal receives the input voltage through a second resistor. The first input terminal is also connected to the first transistor and the ground terminal, and the second input terminal is also connected to the first constant current source and the output terminal of the operational amplifier is connected to the control terminals of the first transistor and the second transistor.

[0021] The current of the second transistor is mirrored and proportional to the current of the first transistor, and the second transistor outputs the first current.

[0022] Optionally, the pull-up current generating unit includes a current mirror and a second constant current source. The second constant current source outputs the second preset current. The output terminal of the second constant current source is connected to the output terminal of the first current generating unit and the input terminal of the current mirror, respectively. The output terminal of the current mirror is connected to the gate of the power transistor, and the current mirror outputs the pull-up current.

[0023] Optionally, the pull-down current generating unit includes a third transistor, the first terminal of which is connected to the gate of the power transistor, the second terminal of which is grounded, and the control terminal of which is connected to the output terminal of the operational amplifier. The current of the third transistor is the pull-down current.

[0024] The present invention also proposes a switching power supply, including a power circuit and any of the above-described redundant circuits, wherein the redundant circuit is connected between the output terminal of the power circuit and the load.

[0025] Compared with the prior art, the present invention has the following advantages: The present invention can autonomously adjust the drive current of the power transistor according to the relationship between the input voltage and the output voltage of the power transistor in the redundant circuit. Under heavy load or startup, the power transistor can be turned on quickly. Under no-load, it does not consume the drive current of the power transistor. Under light load, the drive current consumption is low and the power consumption is small. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a redundant circuit;

[0027] Figure 2 This is a block diagram of the driving circuit for the redundant circuit of the present invention;

[0028] Figure 3 for Figure 2 Schematic diagram of an embodiment of the driving circuit;

[0029] Figure 4 This is a graph showing the relationship between the power transistor drive current and the difference between the input voltage and the output voltage.

[0030] Figure 5 To introduce Figure 1 The schematic diagram of a redundant circuit switching converter. Detailed Implementation

[0031] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the present invention.

[0032] To provide the public with a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the invention, but those skilled in the art can fully understand the invention without these details.

[0033] See Figure 1 In the front-end circuit of redundant circuits (such as power conversion circuits, see...) Figure 5 During normal operation, the power transistor M1 in the redundant circuit is turned on, and the load receives power normally. When the load is unloaded, the power transistor M1 is turned off. The first terminal of the power transistor receives the input voltage VIN generated by the front-end circuit, and the second terminal of the power transistor is connected to the output capacitor COUT and the load. The voltage at the second terminal of the power transistor is the system output voltage VOUT. (See also...) Figure 5 This diagram illustrates a switching converter with redundant circuitry. The switching converter converts AC voltage to input voltage VIN (the output voltage of the power conversion circuit) via a power conversion circuit. The redundant circuitry is connected between the input voltage VIN and the load. The output capacitor COUT is connected in parallel with the load. Under different load conditions, the redundant circuitry operates in different states based on the voltage difference between the input and output voltages. To optimize the power consumption of the power transistor drive circuit in the redundant circuitry, this invention is designed as follows... Figure 2 The driving circuit shown.

[0034] See Figure 2 This diagram illustrates the block diagram of the power transistor drive circuit in a redundant circuit. The drive current is generated based on the voltage difference (VIN-VOUT) across the power transistor to turn the power transistor M1 on / off. When the load is unloaded, the voltages VIN and VOUT across the power transistor are equal, the drive current is zero, the power transistor is turned off, and there is no drive current consumption, thus optimizing static power consumption. When the load is heavy (the load is greater than the heavy load reference), the output voltage VOUT is much smaller than the input voltage VIN, resulting in a larger pull-up current to quickly turn on the power transistor. When the load is light (the load is less than the heavy load reference and not unloaded), VIN-VOUT is controlled to a preset difference. When the system is stable, the pull-up current equals the pull-down current equals the preset current. Setting a suitable, smaller preset current can optimize drive power consumption. Specifically, the drive circuit includes a first current generation unit, a pull-up current generation unit, and a pull-down current generation unit. The first current generation unit generates a first current I1 based on the voltage difference between the input voltage VIN and the output voltage VOUT. The pull-up current generation unit generates a pull-up current I2 for the power transistor gate based on the first current I1. The pull-down current generation unit generates a pull-down current I3 for the power transistor gate based on the voltage difference between the input voltage VIN and the output voltage VOUT. See also... Figure 2Taking an NMOS transistor as an example, when the load is unloaded, the load does not consume energy, the output voltage is equal to the input voltage, the first current is proportional to the given first preset current, the pull-up current is zero, the pull-down current is proportional to the first current, and the gate voltage of the power transistor is pulled down to the source potential of the power transistor. After the power transistor is turned off, the pull-down current is zero. When the load is heavy (the load is greater than the heavy load reference), the output voltage is much smaller than the input voltage, the pull-up current is proportional to the given second preset current, and the pull-down current is zero. The pull-up current quickly pulls up the gate voltage of the power transistor to enable the power transistor to turn on quickly. When the load is light (less than the heavy load reference and not unloaded), the pull-up current and pull-down current are generated according to the difference between the input voltage and the output voltage. After the power transistor is turned on and stabilized, the pull-down current is equal to the pull-up current. The difference between the input voltage and the output voltage can be controlled at the preset voltage through loop control so that the pull-up current and pull-down current can be set to the expected current.

[0035] See Figure 3 This indicates Figure 2 The schematic diagram of the driving circuit shows that the first current generation circuit includes operational amplifier 01, first resistor R1, second resistor R2, first constant current source Is1, transistor M1, and transistor M2. The first input terminal of operational amplifier 01 receives the output voltage VOUT through resistor R1 and is connected to the ground terminal via transistor M1. The current flowing through transistor M1 is I0. The second input terminal of operational amplifier 02 receives the input voltage VIN through resistor R2 and is connected to the ground terminal via the first constant current source Is1. Transistor M2 and transistor M1 form the first current mirror. Transistors M1 and M2 share a common gate and are connected to the output terminal of operational amplifier 01. Transistors M1 and M2 share a common source. The drain of transistor M2 is connected to potential B, and the current flowing through the transistor is the first current I1. Based on the virtual short characteristic of the op-amp, the potentials of the two input terminals of the op-amp are equal, and thus VOUT-R1*I0=VIN-R2*Is1, I0=(VOUT-VIN+R2*Is1) / R1. If the size ratio of transistor M2 to transistor M1 is K0 (K0 is a constant greater than zero), then when the op-amp output is greater than zero, we have I1=K0*I0=K0*(VOUT-VIN+R2*Is1) / R1, and further I1=K1*(VOUT-VIN)+K2*Is1, K1=K0 / R1, K2=K0*R2 / R1, where K1 and K2 are both constants greater than zero.

[0036] The pull-up current generation unit is a current mirror circuit used to mirror the difference between the second preset current and the first current and output it to the gate of the power transistor. Specifically, it includes a second constant current source Is2. The difference between the second constant current source and the first current is input to a second current mirror composed of transistors M3 and M4. The output current of the second current mirror (the current of transistor M4) is input to a second current mirror composed of transistors P1 and P2. The output current of the second current mirror (the current of transistor P2) is the pull-up current I2. When the second preset current output by the second constant current source is greater than the first current, I2 = K3*(Is2-I1), where K3 is a constant greater than zero. The supply voltage VDD of the pull-up current generation unit is greater than VIN. The VIN voltage is boosted (e.g., through a charge pump circuit) to obtain VDD. The pull-down current generation unit includes a clamping unit and transistor M5. Transistor M5 and transistor M2 form a current mirror with a common source and common gate, and their size ratio is K4. The drain of transistor M5 is connected to the gate of the power transistor. When transistor M5 is turned on, the pull-down current flowing through transistor M5 is I3 = K4 * I1, where K4 is a constant greater than zero. When the gate voltage of the power transistor drops to the source voltage, the clamping unit clamps the gate voltage at the source voltage (to prevent the gate voltage from being continuously pulled down, which would cause an excessive negative voltage between the gate and source and damage the power transistor).

[0037] When the load is unloaded, no energy is consumed, so VOUT = VIN and I1 = K2 * Is1. If K2 * Is1 is set greater than Is2, the current flowing into the second current mirror (transistor M3) is zero, and the pull-up current I2 is zero. If the load is switched from loaded to unloaded, since the power transistor gate has a certain driving voltage when loaded, transistor M5 turns on. The turn-on of M5 generates a pull-down current I3 = K4 * I1 = K4 * K2 * Is1 (generated from the gate voltage during the previous loaded state), rapidly pulling down the gate voltage of the power transistor. After the gate voltage is quickly pulled to the source voltage of the power transistor, the power transistor is turned off. The clamping unit clamps the gate voltage at the source voltage. The clamping unit is disconnected from transistor M5, the drain voltage of transistor M5 is zero, and transistor M5 enters the cutoff region (the drain-source voltage of M5 is zero) and is turned off. The pull-down current I3 is zero. If the load is unloaded when the system starts, there is no driving voltage on the gate of the power transistor. The pull-up current and pull-down current are always zero. Therefore, in the unloaded state, the pull-up current and pull-down current do not consume energy, but only consume a fixed preset current, which greatly optimizes the power consumption of the drive circuit.

[0038] When the load is heavy / full, VOUT is much smaller than VIN, the output voltage of the op-amp is zero, the gate voltages of transistors M1 and M2 are zero, the first current I1 is zero, the pull-down current I3 is zero, and the pull-up current I2 = K3 * Is2 reaches its maximum, so as to quickly pull up the gate voltage of the power transistor (the gate voltage is close to VDD and greater than the source voltage VIN) to quickly turn on the power transistor until the power transistor is fully turned on. Therefore, this invention can improve the turn-on speed of the power transistor under heavy load.

[0039] When the load is light, the first current I1 = K1*(VOUT-VIN) + K2*I0, and VOUT-VIN is greater than zero. VOUT-VIN can be controlled at the preset voltage VFW through loop control. The pull-up current I2 = K3*(Is2-I1) and the pull-down current I3 = K4*I1. After the power transistor is turned on and stabilized, I3 = I2 = INormal, where INormal is the preset current. K3*(Is2-I1) = K4*I1 = INormal. By setting appropriate parameters, the pull-up current and pull-down current can be kept at a small value, resulting in lower drive current consumption compared to existing technologies.

[0040] See Figure 4 This graph illustrates the relationship between the drive current of the power transistor and the voltage difference between the input and output voltages. The horizontal axis represents the magnitude of VIN-VOUT, and the vertical axis represents the drive current I. Gate Size, I Gate When I is greater than 0, it indicates that the drive current is a pull-up current, used to pull up the gate voltage of the power transistor to turn it on. Gate When the value is less than 0, it indicates that the drive current is a pull-down current, used to pull down the gate voltage of the power transistor to turn it off. When VIN-VOUT = 0, the load is unloaded, and the magnitude of the drive current, i.e., the pull-down current, is K4*K2*Is1. Under light load, the pull-up current equals the pull-down current, and the drive current I... Gate When the current is zero, VIN - VOUT = VFW. Under full load / heavy load, the drive current, i.e., the pull-up current, reaches the maximum current K3*Is2. Based on the requirements for the first current under no-load, the requirements for the pull-up current under heavy load / full load, and the relationship between the pull-up and pull-down currents under light load, determine the appropriate values ​​for K1, K2, K3, K4, Is1, and Is2. These parameters can also be adjusted according to response speed, power transistor manufacturing process deviation, circuit area, etc., so that the drive capability and losses of the power transistor can meet the requirements under different load conditions.

[0041] This invention dynamically and autonomously adjusts the driving capability of the power transistors in a redundant circuit based on the voltage difference between VIN and VOUT. Under heavy load or system startup, it generates a large pull-up current to quickly turn on the power transistors. Under no-load conditions, it consumes only a small preset current, without using the power transistors' drive current. Under light load conditions, it sets VIN-VOUT to a preset voltage to adjust the pull-up and pull-down currents of the power transistors to appropriate values. This invention optimizes the driving capability and power consumption of the power transistors in a redundant circuit.

[0042] The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are in a simplified form and use non-precise proportions, in order to facilitate and clearly illustrate the purpose of the embodiments of the invention.

[0043] Although the embodiments are described and illustrated separately above, some common technologies are involved. Those skilled in the art can replace and integrate them between the embodiments. If there is any content not explicitly described in one embodiment, then another embodiment that is described can be referred to.

[0044] The embodiments described above do not constitute a limitation on the scope of protection of this technical solution. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the above embodiments should be included within the scope of protection of this technical solution.

Claims

1. A redundant circuit, comprising a power transistor and its driving circuit, wherein a first terminal of the power transistor receives an input voltage and a second terminal is connected to a load to generate an output voltage, characterized in that... The driving circuit includes: The first current generating unit generates a first current based on the difference between the input voltage and the output voltage and a first preset current; The pull-up current generating unit generates a pull-up current based on the difference between the second preset current and the first current; A pull-down current generating unit generates a pull-down current based on the first current and the pull-up current; The difference between the pull-up current and the pull-down current is used to drive the power transistor. When the load is unloaded, the difference between the second preset current and the first current is less than or equal to zero, so that both the pull-up current and the pull-down current are zero.

2. The redundant circuit according to claim 1, characterized in that: The first current is proportional to the first preset current.

3. The redundant circuit according to claim 1, characterized in that: When the load is greater than the heavy load reference, the pull-up current is proportional to the first preset current.

4. The redundant circuit according to claim 3, characterized in that: The first current and the pull-down current are both zero.

5. The redundant circuit according to claim 1, characterized in that: When the load is less than the heavy load reference and the load is not unloaded, when the redundant circuit enters a steady state, the pull-up current is equal to the pull-down current and equal to the preset current.

6. The redundant circuit according to claim 5, characterized in that: The difference between the input voltage and the output voltage is a preset voltage difference.

7. The redundant circuit according to claim 1, characterized in that: When the load is less than the heavy load reference, the first current is equal to K1×(VOUT-VIN)+K2×Is1, where VOUT is the output voltage, VIN is the input voltage, Is1 is the first preset current, and K1 and K2 are preset constants greater than zero.

8. The redundant circuit according to claim 1, characterized in that: When the load is not unloaded, the pull-up current is K3×(Is2-I1), where Is2 is the second preset current, I1 is the first current, and K3 is a constant greater than zero.

9. The redundant circuit according to claim 1, characterized in that: The first current generating unit includes an operational amplifier, a first constant current source, a first transistor, and a second transistor, wherein the first constant current source outputs the first preset current; The first input terminal of the operational amplifier receives the output voltage through a first resistor, and the second input terminal receives the input voltage through a second resistor. The first input terminal is also connected to the first transistor and the ground terminal, and the second input terminal is also connected to the first constant current source and the output terminal of the operational amplifier is connected to the control terminals of the first transistor and the second transistor. The current of the second transistor is mirrored and proportional to the current of the first transistor, and the second transistor outputs the first current.

10. The redundant circuit according to claim 9, characterized in that: The pull-up current generating unit includes a current mirror and a second constant current source. The second constant current source outputs the second preset current. The output terminal of the second constant current source is connected to the output terminal of the first current generating unit and the input terminal of the current mirror, respectively. The output terminal of the current mirror is connected to the gate of the power transistor, and the current mirror outputs the pull-up current.

11. The redundant circuit according to claim 10, characterized in that: The pull-down current generating unit includes a third transistor. The first terminal of the third transistor is connected to the gate of the power transistor, the second terminal is grounded, and the control terminal is connected to the output terminal of the operational amplifier. The current of the third transistor is the pull-down current.

12. A switching power supply, characterized in that: It includes a power circuit and a redundant circuit as described in any one of claims 1-11, wherein the redundant circuit is connected between the output of the power circuit and the load.

Images