TWI444804B - Output current detecting device and method of voltage regulator - Google Patents

Description

Output current detecting device and method for voltage regulator

The present invention relates to a voltage regulator, and more particularly to an output current detecting device and method for a voltage regulator applied to a charger.

When a voltage regulator is used to provide a regulated current, such as a charger, a commonly used output current detection method is to connect a detection resistor in series with the inductance of the voltage regulator. Referring to FIG. 1, the output current of the voltage regulator Io Through the detection resistor Rsense, such as the US patent No. 3369561, LTC4001 or SMB135, the voltage change on the detection resistor Rsense is related to the output current Io, and has a fixed ratio of 1:1 to the output current Io. The voltage change on the resistor Rsense is differentially input to the controller 12 via the error amplifier 10 for feedback control to control the driver 14 to switch the power transistor.

Since the conventional detection method is to set the detection resistor Rsense in the charging path of the voltage regulator, in order to reduce the loss of the detection resistor Rsense on the output power, the detection resistor Rsense must be a low resistance precision resistor, but a low resistance value. The detectable voltage change is small, sensitive to noise, and susceptible to noise interference.

The invention provides an output current detecting device and method for a voltage regulator, which sets a detecting resistor outside a charging path, reduces the influence on the output power, and accurately detects the change of the output terminal for feedback control of the voltage regulator. .

One of the objects of the present invention is to provide an output current detecting device for a voltage regulator.

One of the objects of the present invention is to provide a method for detecting an output current of a voltage regulator.

One of the objects of the present invention is to provide a voltage regulator having an output current detecting function.

According to the present invention, an output current detecting device of a voltage regulator includes a sensing circuit that senses an upper bridge transistor of the voltage regulator and a current of the lower bridge transistor to generate a first current and a second a current, a summing circuit sums the first and second currents to generate a sum current, and a set resistor is coupled to the summing circuit to detect a change in the sum current, and a voltage change on the set resistor is provided to the controller Do feedback control.

Alternatively, the current of the upper bridge transistor is sensed and the combined current is generated by analog circuit simulation.

2 is a first embodiment of the present invention, the upper bridge transistor 26 is connected between the input voltage Vi and the switching node SW, and the lower bridge transistor 28 is connected between the switching node SW and the ground potential GND, and an inductive connection switching node SW The upper bridge transistor 26 and the lower bridge transistor 28 are controlled to be switched by the driver 30 to generate an output current Io flowing through the inductor and generating an output voltage Vo at the output. The upper bridge detecting circuit 20 senses the current of the upper bridge transistor 26 and generates a current I1. The lower bridge detecting circuit 22 senses the current of the lower bridge transistor 28 to generate a current I2, and the current I1 and the current I2 are summed. After the circuit 24 is summed up, it is supplied to the set resistor Rset. The proportional relationship between the currents I1 and I2 and the output current Io in this embodiment is no longer fixed to 1:1, and the ratio of the upper and lower bridge currents can also be adjusted. For example, the proportional relationship between the upper and lower bridge currents is adjusted by K1 and K2, The current flowing through the set resistor Rset is always expressed as Io/K3, and K1 and K2 can be adjusted according to actual needs to achieve the purpose of eliminating offset or delay. Comparator 34 detects the voltage change at node A and compares it with reference voltage Vref to provide feedback control to controller 32. Since the set resistance Rset is not in the charging path of the voltage regulator, the resistance of the set resistor Rset can be increased, and the voltage change of the node A is more obvious, so that the use of the precision resistor can be avoided, the cost is reduced, and the noise is less likely to be disturbed.

The voltage regulator is applied to the charger with an over current protect (OCP) mechanism or a zero current detection mechanism to monitor the current on the power transistor to provide protection when the output current is too high or too low. The present invention utilizes these original detection mechanisms as the upper bridge detection circuit 20 and the lower bridge detection circuit 22, and monitors the change of the output current Io for feedback control.

3 is an embodiment of the summing circuit 24 of FIG. 2. The slope of the current I1 (Psense output) waveform generated by the upper bridge detecting circuit 20 is Vi/L, and the current I2 generated by the lower bridge detecting circuit 22 (Nsense output). The slope of the waveform is (Vo-Vi)/L, and the summing circuit 24 adds up the current Io/K shown in the lower part of FIG. 3, flows through the set resistor Rset and generates a voltage at the node A.

4 is a second embodiment of the present invention in which a current detecting device of the present invention is provided in a non-synchronous buck voltage converter. In this embodiment, the current on the diode D is not detected, and only the current on the upper bridge transistor 40 is sensed by the sensing circuit 42 and then generated by the current analog circuit 44 to generate a current waveform as shown in FIG. Set the resistance Rset and monitor the voltage change on the set resistor Rset for feedback control (not shown). In other embodiments, the current flowing through the diode D may be directly detected without being simulated, and the current of the upper bridge transistor is summed and supplied to the set resistor Rset.

5 is a third embodiment of the present invention. The sensing device 56 detects the current of the upper bridge transistor 54 of the boost voltage converter, generates a current I1, and the sensing device 58 detects the boost voltage converter. The current of the bridge transistor 52 generates a current I2. The current I1 and the current I2 are summed by the summing circuit 60 to sense the current Is, and a voltage is generated at the node B for comparison by the comparator 66 with the reference voltage Vref to provide Controller 64 performs feedback control to cause driver 62 to generate drive signals to upper and lower bridge transistors 54 and 52. In this embodiment, the currents I1 and I2 can also be scaled by K4 and K5.

6 is a variation of the embodiment of FIG. 5, and the reciprocal of K5 is designed to be 0. In other words, only the current change of the upper bridge transistor 54 is sensed, thereby generating a sense current Is to the set resistance Rset, and monitoring the output voltage Vo. Variety.

In other embodiments, the output current detecting device of the present invention can also be applied to other types of voltage converters, such as a buck-boost type, a back-pressure type, and the like.

The above description of the preferred embodiments of the present invention is intended to be illustrative, and is not intended to limit the scope of the invention to the disclosed embodiments. It is possible to make modifications or variations based on the above teachings or learning from the embodiments of the present invention. The embodiments are described and illustrated in the practical application of the present invention in various embodiments, and the technical idea of the present invention is intended to be equivalent to the scope of the following claims. Decide.

10. . . Error amplifier

12. . . Controller

14. . . driver

20. . . Upper bridge detection circuit

twenty two. . . Lower bridge detection circuit

twenty four. . . Addition circuit

26. . . Upper bridge transistor

28. . . Lower bridge transistor

30. . . driver

32. . . Controller

34. . . Comparators

40. . . Upper bridge transistor

42. . . Sense circuit

44. . . Current analog circuit

50. . . Step-up voltage converter

52. . . Lower bridge transistor

54. . . Upper bridge transistor

56. . . Sense circuit

Figure 1 is a schematic diagram of a conventional voltage converter;

Figure 2 is a schematic view of a first embodiment of the present invention;

Figure 3 is a schematic diagram of the summing circuit of Figure 2;

Figure 4 is a schematic view of a second embodiment of the present invention;

Figure 5 is a schematic view of a third embodiment of the present invention;

Figure 6 is a variation of the embodiment of Figure 5.

20. . . Upper bridge detection circuit

twenty two. . . Lower bridge detection circuit

twenty four. . . Addition circuit

26. . . Upper bridge transistor

28. . . Lower bridge transistor

30. . . driver

32. . . Controller

34. . . Comparators

Claims (22)

An output current detecting device for a voltage regulator, the voltage regulator comprising an upper bridge component, a lower bridge component, and an inductor, the three are commonly coupled to a switching node, and the other ends of the three are respectively coupled to an input end and a The ground potential is coupled to an output terminal, and a controller controls switching of the upper bridge and the lower bridge component to generate an output voltage at the output end. The output current detecting device includes: a sensing circuit that senses the upper The current of the bridge component generates a sense current; an analog circuit generates a sum current according to the sense current; and a set resistor detects a change of the sum current; wherein the voltage change on the set resistor is provided to The controller does feedback control. The output current detecting device of claim 1, wherein the sensing circuit is part of an overcurrent protection mechanism or a zero current protection mechanism of the voltage regulator. The output current detecting device of claim 1, wherein one end of the setting resistor is connected to the analog circuit, and the other end is grounded. The output current detecting device of claim 1, wherein the upper and lower bridge components are all transistors. The output current detecting device of claim 1, wherein the upper bridge component is a transistor and the lower bridge component is a diode. The output current detecting device of claim 1, wherein the upper bridge component is coupled between the input terminal and the switching node, the lower bridge component is coupled between the ground potential and the switching node, and the inductor is coupled to Between the output and the switching node. The output current detecting device of claim 1, wherein the upper bridge component is coupled between the output terminal and the switching node, the lower bridge component is coupled between the ground potential and the switching node, and the inductor is coupled to Between the input and the switching node. The output current detecting device of claim 1, wherein the upper bridge component is coupled between the input terminal and the switching node, the lower bridge component is coupled between the output terminal and the switching node, and the inductor is coupled to The ground potential is between the switching node. A method for detecting an output current of a voltage regulator, the voltage regulator comprising an upper bridge component, a lower bridge component, and an inductor, the three are commonly coupled to a switching node, and the other ends of the three are respectively coupled to an input terminal and a The ground potential is coupled to an output terminal, and a controller controls switching of the upper bridge component and the lower bridge component to generate an output voltage at the output terminal. The output current detection method includes the following steps: sensing the upper bridge component Current to generate a sense current; generate a sum current according to the sense current; provide the sum current to a set resistor; and provide a voltage change on the set resistor to the controller for feedback control . The output current detecting method of claim 9, wherein the upper and lower bridge components are all transistors. The output current detecting method of claim 9, wherein the upper bridge component is a transistor and the lower bridge component is a diode. The output current detecting method of claim 9, wherein the upper bridge component is coupled between the input terminal and the switching node, the lower bridge component is coupled between the ground potential and the switching node, and the inductor is coupled to Between the output and the switching node. The output current detecting method of claim 9, wherein the upper bridge component is coupled between the output terminal and the switching node, the lower bridge component is coupled between the ground potential and the switching node, and the inductor is coupled to Between the input and the switching node. The output current detecting method of claim 9, wherein the upper bridge component is coupled between the input terminal and the switching node, the lower bridge component is coupled between the output terminal and the switching node, and the inductor is coupled to The ground potential is between the switching node. A voltage regulator includes: an upper bridge component, a lower bridge component, and an inductor, wherein the three are coupled to a switching node, and the other ends of the three are coupled to an input terminal, a ground potential, and an output terminal; a controller for controlling switching of the upper bridge component and the lower bridge component to generate an output voltage at the output terminal; a sensing circuit sensing current of the upper bridge component to generate a sensing current; an analog circuit, according to The sense current simulation generates a sum current; and a set resistor detects a change in the sum current; wherein the voltage change on the set resistor is provided to the controller for feedback control. The voltage regulator of claim 15, wherein the sensing circuit is part of an overcurrent protection mechanism or a zero current detection mechanism of the voltage regulator. The voltage regulator of claim 15, wherein one end of the set resistor is connected to the analog circuit and the other end is grounded. The voltage regulator of claim 15, wherein the upper and lower bridge elements are all transistors. The voltage regulator of claim 15, wherein the upper bridge component is a transistor and the lower bridge component is a diode. The voltage regulator of claim 15, wherein the upper bridge component is coupled between the input terminal and the switching node, the lower bridge component is coupled between the ground potential and the switching node, and the inductor is coupled to the output Between the end and the switching node. The voltage regulator of claim 15, wherein the upper bridge component is coupled between the output terminal and the switching node, the lower bridge component is coupled between the ground potential and the switching node, and the inductor is coupled to the input Between the end and the switching node. The voltage regulator of claim 15, wherein the upper bridge component is coupled between the input terminal and the switching node, the lower bridge component is coupled between the output terminal and the switching node, and the inductor is coupled to the ground The potential and the switching node.