Current sensing circuit suitable for metal oxide semiconductor field effect transistor circuit

Abstract

A current sensing circuit includes an output driving transistor having an output node to provide an output voltage; a diode connection type first transistor connected between the output node and the current circuit; a second transistor and a third transistor are connected in series with each other, a gate of the second transistor is connected to a gate of the output driving transistor, and a gate of the third transistor is connected to a gate of the first transistor; and the current measuring circuit is connected in series with the second transistor and the third transistor and is used for measuring the current flowing through the second transistor and the third transistor.

Description

Technical Field

[0001] The present invention relates to a current sensing circuit, and more particularly to a current sensing circuit suitable for a metal oxide semiconductor field effect transistor (MOSFET) circuit. Background Art

[0002] A current sensing circuit is a device that measures the current flowing through an electrical conductor. It can be used to monitor and control the amount of current flowing in a circuit. Current sensing circuits can be applied to metal-oxide-semiconductor field-effect transistor (MOSFET) circuits, such as MOSFET switches or MOSFET output stages. They can be used for overcurrent protection, direct current (DC) charge and discharge current protection, and current feedback sensing in power integrated circuits (ICs).

[0003] There are several types of current sensing circuits, such as shunt resistors and Hall effect sensors. Shunt resistors are the most common type of current sensing circuit and operate by measuring the voltage drop across a resistor in series with the load. This voltage drop is proportional to the current flowing through the resistor and can be measured using an amplifier circuit.

[0004] The Hall effect sensor is another type of current sensing circuit used to measure AC and DC current. It works by measuring the magnetic field generated by the current flowing through a conductor. The magnetic field causes a change in the sensor's output voltage, which can be measured by an amplifier circuit.

[0005] However, Hall-effect sensors are bulky and susceptible to noise. Shunt resistor current sensing circuits require a small resistor to convert the current signal to a voltage, and they also require an amplifier circuit and noise filtering. Current sensing also has low resolution and requires a voltage drop across the resistor path.

[0006] One method of implementing a current sensing circuit is to use a step-up DC-DC converter. This method requires a series precision resistor for current feedback control and converts the series resistor into a voltage measurement, which results in additional power loss.

[0007] Another approach to implementing a current sensing circuit is to use an operational amplifier (OPA) to feed back the current detection circuit. However, this approach has limitations in the OPA's operating bandwidth and quiescent current consumption. Furthermore, adding an OPA circuit increases the overall cost of the circuit.

[0008] For the reasons mentioned above, there is an urgent need for a high-speed and low-latency current sensing circuit. This circuit can be used for overcurrent protection, current feedback in power integrated circuits, or current measurement in the output stage of an operational amplifier. Summary of the Invention

[0009] In view of the foregoing, one objective of embodiments of the present invention is to provide a high-speed, low-latency current sensing circuit that simultaneously meets the requirements for high-precision current detection. The current sensing circuit eliminates the need for a series resistor structure to sense the current in a shunt detection circuit and eliminates the need for an operational amplifier structure to achieve high-speed current detection.

[0010] According to one embodiment of the present invention, a current sensing circuit includes an output driver transistor, a first transistor, a second transistor, a third transistor, and a current measurement circuit. The output driver transistor has an output node for providing an output voltage. The first transistor is diode-connected and connected between the output node and the current circuit. The second and third transistors are connected in series, with the gate of the second transistor connected to the gate of the output driver transistor, and the gate of the third transistor connected to the gate of the first transistor. The current measurement circuit is connected in series with the second and third transistors to measure the current flowing through the second and third transistors.

[0011] According to one embodiment of the present invention, the current circuit includes a current source.

[0012] According to one embodiment of the present invention, the output driver transistor includes a P-type metal oxide semiconductor field effect transistor, the first transistor includes a P-type metal oxide semiconductor field effect transistor, the second transistor includes a P-type metal oxide semiconductor field effect transistor, and the third transistor includes a P-type metal oxide semiconductor field effect transistor.

[0013] According to one embodiment of the present invention, the source of the output driver transistor is connected to the power supply, and the drain of the output driver transistor is connected to the output node; the source of the first transistor is connected to the output node, and the drain of the first transistor is connected to the current circuit; the source of the second transistor is connected to the power supply, and the drain of the second transistor is connected to the source of the third transistor; and the drain of the third transistor is connected to the current measurement circuit.

[0014] According to one embodiment of the present invention, the output driver transistor includes an N-type metal oxide semiconductor field effect transistor, the first transistor includes a P-type metal oxide semiconductor field effect transistor, the second transistor includes an N-type metal oxide semiconductor field effect transistor, and the third transistor includes a P-type metal oxide semiconductor field effect transistor.

[0015] According to one embodiment of the present invention, the drain of the output driver transistor is connected to the power supply, and the source of the output driver transistor is connected to the output node; the source of the first transistor is connected to the output node, and the drain of the first transistor is connected to the current circuit; the drain of the second transistor is connected to the power supply, and the source of the second transistor is connected to the source of the third transistor; and the drain of the third transistor is connected to the current measurement circuit.

[0016] According to one embodiment of the present invention, the current circuit includes a fourth transistor.

[0017] According to one embodiment of the present invention, the fourth transistor comprises an N-type metal oxide semiconductor field effect transistor, a drain of the fourth transistor is connected to the drain of the first transistor, a source of the fourth transistor is connected to ground, and a gate of the fourth transistor is coupled to receive a bias voltage.

[0018] According to one embodiment of the present invention, the current measurement circuit includes a resistor connected between the drain of the third transistor and ground, and an analog-to-digital converter for converting the voltage across the resistor into a digital signal to obtain the current flowing through the second transistor and the third transistor.

[0019] According to one embodiment of the present invention, it further comprises:

[0020] The replica second transistor and the replica third transistor are connected in series between a power source and the current circuit. The gates of the replica second transistor and the replica third transistor are connected to the gates of the second transistor and the third transistor respectively.

[0021] According to one embodiment of the present invention, the replica second transistor includes a P-type metal oxide semiconductor field effect transistor, and the replica third transistor includes a P-type metal oxide semiconductor field effect transistor. The source of the replica second transistor is connected to a power supply, the drain of the replica second transistor is connected to the source of the replica third transistor, and the drain of the replica third transistor is connected to the current circuit.

[0022] According to one embodiment of the present invention, the current circuit includes a current mirror circuit including a fourth transistor and a diode-connected fifth transistor.

[0023] According to one embodiment of the present invention, the fourth transistor includes an N-type metal oxide semiconductor field effect transistor, and the fifth transistor includes an N-type metal oxide semiconductor field effect transistor, the drain of the fourth transistor is connected to the drain of the first transistor, the source of the fourth transistor is connected to ground, and the gate of the fourth transistor is coupled to receive a bias voltage; the drain of the fifth transistor is connected to the drain of the replica third transistor and the gate of the fourth transistor, and the source of the fifth transistor is connected to ground.

[0024] According to one embodiment of the present invention, the current measurement circuit includes a resistor connected between the drain of the third transistor and ground.

[0025] According to one embodiment of the present invention, the output driver transistor includes an N-type metal oxide semiconductor field effect transistor, the first transistor includes an N-type metal oxide semiconductor field effect transistor, the second transistor includes an N-type metal oxide semiconductor field effect transistor, and the third transistor includes an N-type metal oxide semiconductor field effect transistor.

[0026] According to one embodiment of the present invention, the device further includes a DC-DC converter coupled to the first transistor, the second transistor, and the third transistor.

[0027] According to one embodiment of the present invention, the DC-DC converter comprises:

[0028] an inductor connected in series with the output driver transistor between a power supply and a ground, wherein a connection node between the inductor and the output driver transistor is connected to the drain of the first transistor, and a gate of the output driver transistor is connected to the gate of the second transistor;

[0029] a Zener diode having an anode connected to the connection node;

[0030] at least one capacitor connected between the cathode of the Zener diode and ground; and

[0031] A pulse width modulation controller, serving as the current measurement circuit, for generating a control signal to be provided to the gate of the output drive transistor;

[0032] The pulse width modulation controller is controlled by the voltage feedback of the cathode of the Zener diode and the current feedback of the source of the third transistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1A A circuit diagram showing a current sensing circuit according to an embodiment of the present invention is shown, which is applicable to a metal oxide semiconductor field effect transistor circuit.

[0034] Figure 1B A circuit diagram showing a current sensing circuit according to another embodiment of the present invention is shown, which is applicable to a MOSFET circuit.

[0035] Figure 2 A circuit diagram showing a current sensing circuit according to a first embodiment of the present invention.

[0036] Figure 3 A circuit diagram showing a current sensing circuit according to a second embodiment of the present invention.

[0037] Figure 4A circuit diagram showing a current sensing circuit according to a third embodiment of the present invention.

[0038] Reference numerals:

[0039] 100: Current sensing circuit

[0040] 10: Load

[0041] 11: Current Circuit

[0042] 12: Current measurement circuit

[0043] 13: Input stage circuit

[0044] 14:Analog to Digital Converter

[0045] 15: DC to DC converter

[0046] 151: Pulse Width Modulation Controller

[0047] 152:Amplifier

[0048] Vout: output voltage

[0049] Vbias: bias voltage

[0050] MOSO: Output driver transistor

[0051] MOS1: first transistor

[0052] MOS2: Second transistor

[0053] MOS2B: Copy the second transistor

[0054] MOS3: The third transistor

[0055] MOS3B: Replicated third transistor

[0056] MOS4: the fourth transistor

[0057] MOS5: Fifth transistor

[0058] R: Resistor

[0059] L: Inductor

[0060] D: Zener diode

[0061] C: Capacitor DETAILED DESCRIPTION

[0062] Figure 1AThe circuit diagram of a current sensing circuit 100 according to an embodiment of the present invention is suitable for use in a metal-oxide-semiconductor field-effect transistor (MOSFET) circuit, such as a MOSFET switch or a MOSFET output stage, but is not limited thereto. Current sensing circuit 100 can be used for overcurrent protection, direct current (DC) charge and discharge current protection, and current feedback sensing in power integrated circuits (ICs).

[0063] In this embodiment, the current sensing circuit 100 may include an output driver transistor MOS0 (of the output stage) connected between a power supply and an output node providing an output voltage Vout. The current sensing circuit 100 may include a first transistor MOS1 in a diode-connected configuration (with its gate and drain connected) connected between the output node and a current circuit 11 (e.g., a current source). The current sensing circuit 100 may include a second transistor MOS2 and a third transistor MOS3 connected in series with a current measurement circuit 12 for measuring the current flowing through the second transistor MOS2 and the third transistor MOS3. The gate of the second transistor MOS2 is connected to the gate of the output driver transistor MOS0, and the gate of the third transistor MOS3 is connected to the gate of the first transistor MOS1. It is noteworthy that the voltage at the connection node between the second transistor MOS2 and the third transistor MOS3 (i.e., the source of the third transistor MOS3) is approximately the same as the output voltage Vout because the output voltage Vout (of the output node) minus the threshold voltage Vt (or gate-to-source voltage) of the first transistor MOS1 plus the threshold voltage Vt (or gate-to-source voltage) of the third transistor MOS3 is approximately equal to the output voltage Vout (of the output node). Furthermore, the ratio of the output current of the output driver transistor MOS0 to the current flowing through the second / third transistors MOS2 / 3 can be determined by the size ratio of the output driver transistor MOS0 to the second / third transistors MOS2 / 3 (e.g., m:1). Therefore, if the current flowing through the second / third transistors MOS2 / 3 is I, the current flowing through the output driver transistor MOS0 is mI, and the current flowing to the load 10 is equal to mI minus the current of the current source (of the current circuit 11).

[0064] In this embodiment, the output driver transistor MOSO comprises a P-type metal oxide semiconductor field effect transistor, the first transistor MOS1 comprises a P-type metal oxide semiconductor field effect transistor, the second transistor MOS2 comprises a P-type metal oxide semiconductor field effect transistor, and the third transistor MOS3 comprises a P-type metal oxide semiconductor field effect transistor. The source of the output driver transistor MOSO is connected to the power supply, and the drain thereof is connected to the output node. The source of the first transistor MOS1 is connected to the output node, and the drain thereof is connected to the current circuit 11.

[0065] The source of the second transistor MOS2 is connected to the power supply, and the drain thereof is connected to the source of the third transistor MOS3.

[0066] The drain of the third transistor MOS3 is connected to the current measurement circuit 12 .

[0067] Figure 1B A circuit diagram showing a current sensing circuit 100 according to another embodiment of the present invention is shown, which is applicable to a MOSFET circuit. Figure 1B The current sensing circuit 100 is similar to Figure 1A The current sensing circuit 100 has the following differences.

[0068] In this embodiment, the output driver transistor MOSO comprises an N-type metal oxide semiconductor field effect transistor, the first transistor MOS1 comprises a P-type metal oxide semiconductor field effect transistor, the second transistor MOS2 comprises an N-type metal oxide semiconductor field effect transistor, and the third transistor MOS3 comprises a P-type metal oxide semiconductor field effect transistor. The drain of the output driver transistor MOSO is connected to the power supply, and the source thereof is connected to the output node. The source of the first transistor MOS1 is connected to the output node, and the drain thereof is connected to the current circuit 11.

[0069] The drain of the second transistor MOS2 is connected to the power supply, and the source thereof is connected to the source of the third transistor MOS3.

[0070] The drain of the third transistor MOS3 is connected to the current measurement circuit 12 .

[0071] Figure 2 A circuit diagram of a current sensing circuit 100 according to a first embodiment of the present invention is shown. Figure 2 The current sensing circuit 100 uses Figure 1A The basic circuit architecture is described in detail below.

[0072] The current circuit 11 of this embodiment may include a fourth transistor MOS4. In this embodiment, the fourth transistor MOS4 includes an N-type metal oxide semiconductor field effect transistor. The drain of the fourth transistor MOS4 is connected to (the drain of) the first transistor MOS1, the source of the fourth transistor MOS4 is connected to ground, and the gate of the fourth transistor MOS4 is coupled to receive a bias voltage Vbias. Figure 2 An input stage circuit 13 of an operational amplifier is illustrated.

[0073] In this embodiment, the current measurement circuit 12 may include a resistor R connected between (the drain of) the third transistor MOS3 and ground, and an analog-to-digital converter (ADC) 14 for converting the (analog) voltage across the resistor R into a digital signal, thereby obtaining the current flowing through the second transistor MOS2 and the third transistor MOS3. Therefore, the current can be monitored in real time.

[0074] Figure 3 A circuit diagram of a current sensing circuit 100 according to a second embodiment of the present invention is shown. Figure 3 The current sensing circuit 100 uses Figure 1A The basic circuit architecture is described in detail below.

[0075] In this embodiment, the current sensing circuit 100 may include a replica second transistor MOS2B and a replica third transistor MOS3B connected in series between a power supply and a current circuit 11. The gates of the replica second transistor MOS2B and the replica third transistor MOS3B are connected to the gates of the second transistor MOS2 and the third transistor MOS3, respectively. The replica second transistor MOS2B comprises a P-type metal oxide semiconductor field effect transistor, and the replica third transistor MOS3B comprises a P-type metal oxide semiconductor field effect transistor. The source of the replica second transistor MOS2B is connected to the power supply, and its drain is connected to the source of the replica third transistor MOS3B. The drain of the replica third transistor MOS3B is connected to the current circuit 11.

[0076] In this embodiment, the current circuit 11 may include a current mirror circuit including a fourth transistor MOS4 and a fifth transistor MOS5 of diode-connected type (with its gate and drain connected). In this embodiment, the fourth transistor MOS4 includes an N-type metal oxide semiconductor field effect transistor, and the fifth transistor MOS5 includes an N-type metal oxide semiconductor field effect transistor. The drain of the fourth transistor MOS4 is connected to (the drain of) the first transistor MOS1, its source is connected to ground, and its gate is coupled to receive a bias voltage Vbias. The drain of the fifth transistor MOS5 is connected to the drain of the replica third transistor MOS3B and the gate of the fourth transistor MOS4, and its source is connected to ground.

[0077] In this embodiment, the current measurement circuit 12 may include a resistor R connected between (the drain of) the third transistor MOS3 and ground. Therefore, the voltage across the resistor R can be used for subsequent measurement. It is noteworthy that by setting the size ratios between the output driver transistor MOS0, the fourth / fifth transistors MOS4 / 5, and the second / third transistors MOS2 / 3, the ratio of the output current of the output driver transistor MOS0 to the current flowing through the second / third transistors MOS2 / 3 does not substantially change due to light or heavy loads.

[0078] In one embodiment, the ratio of the output current of the output driver transistor MOS0 to the current flowing through the second / third transistors MOS2 / 3 can be determined by the size ratio (e.g., m:1) of the output driver transistor MOS0 to the first / second / third / replica second / replica third transistors MOS1 / 2 / 3 / 2B / 3B, and the fourth / fifth transistors MOS4 / 5. Therefore, if the current flowing through the second / third / replica second / replica third transistors MOS2 / 3 / 2B / 3B is I, the current flowing through the output driver transistor MOS0 is mI, and the current flowing to the load 10 is equal to (m-1)I.

[0079] In another embodiment, if the size ratio of the fifth transistor MOS5 to the fourth transistor MOS4 is n:1 (instead of 1:1 in the previous example), the current flowing to the load 10 is equal to (m−1 / n)I.

[0080] Figure 4 A circuit diagram of a current sensing circuit 100 according to a third embodiment of the present invention is shown. Figure 4 The current sensing circuit 100 uses Figure 1B The basic circuit structure is the same as that of FIG. 1 , but the first transistor MOS1 and the third transistor MOS3 are replaced by N-type metal oxide semiconductor field effect transistors.

[0081] The current sensing circuit 100 of this embodiment may include a direct current (DC-DC) converter 15 coupled to a first transistor MOS1, a second transistor MOS2, and a third transistor MOS3. The DC-DC converter 15 may include an inductor L connected in series with an output driver transistor MOS0 between a power supply and ground. The connection node between the inductor L and the output driver transistor MOS0 is connected to the drain of the first transistor MOS1. The gate of the output driver transistor MOS0 is connected to the gate of the second transistor MOS2. The DC-DC converter 15 may include a Zener diode D, the anode of which is connected to the connection node (between the inductor L and the output driver transistor MOS0). The DC-DC converter 15 may include at least one capacitor C connected between the cathode of the Zener diode D and ground. The DC-DC converter 15 may include a pulse width modulation (PWM) controller 151 (serving as the current measurement circuit 12) for generating a control signal, which is provided to (the gate of) the output driver transistor MOS0 via an amplifier 152. The pulse width modulation controller 151 is controlled by voltage feedback from the cathode of the Zener diode D and current feedback from (the source of) the third transistor MOS3. Thus, current feedback control is achieved. It is worth noting that the ratio of the current flowing through the output driver transistor MOS0 to the current flowing through the third / second transistor MOS3 / 2 can be determined by the size ratio of the output driver transistor MOS0 to the third / second transistor MOS3 / 2 (e.g., m:1).

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the patent application of the present invention; any other equivalent changes or modifications that do not depart from the spirit disclosed by the invention should be included in the scope of the patent application below.

Claims

1. A current sensing circuit suitable for a metal oxide semiconductor field effect transistor circuit, characterized in that: Include: an output driver transistor having an output node for providing an output voltage; A first transistor having a diode connection type, connected between the output node and the current circuit; A second transistor and a third transistor are connected in series, the gate of the second transistor is connected to the gate of the output driver transistor, and the gate of the third transistor is connected to the gate of the first transistor; and The current measuring circuit is connected in series to the second transistor and the third transistor, and is used for measuring the current flowing through the second transistor and the third transistor.

2. The current sensing circuit for a metal oxide semiconductor field effect transistor circuit as claimed in claim 1, wherein: The current circuit includes a current source.

3. The current sensing circuit for a metal oxide semiconductor field effect transistor circuit as claimed in claim 1, wherein: The output driver transistor includes a P-type metal oxide semiconductor field effect transistor, the first transistor includes a P-type metal oxide semiconductor field effect transistor, the second transistor includes a P-type metal oxide semiconductor field effect transistor, and the third transistor includes a P-type metal oxide semiconductor field effect transistor.

4. The current sensing circuit for a metal oxide semiconductor field effect transistor circuit as claimed in claim 3, wherein: The source of the output driver transistor is connected to the power supply, and the drain of the output driver transistor is connected to the output node; the source of the first transistor is connected to the output node, and the drain of the first transistor is connected to the current circuit; the source of the second transistor is connected to the power supply, and the drain of the second transistor is connected to the source of the third transistor; and the drain of the third transistor is connected to the current measurement circuit.

5. The current sensing circuit applicable to a metal oxide semiconductor field effect transistor circuit as claimed in claim 1, wherein: The output driver transistor includes an N-type metal oxide semiconductor field effect transistor, the first transistor includes a P-type metal oxide semiconductor field effect transistor, the second transistor includes an N-type metal oxide semiconductor field effect transistor, and the third transistor includes a P-type metal oxide semiconductor field effect transistor.

6. The current sensing circuit applicable to a metal oxide semiconductor field effect transistor circuit as claimed in claim 5, wherein: The drain of the output driver transistor is connected to the power supply, and the source of the output driver transistor is connected to the output node; the source of the first transistor is connected to the output node, and the drain of the first transistor is connected to the current circuit; the drain of the second transistor is connected to the power supply, and the source of the second transistor is connected to the source of the third transistor; and the drain of the third transistor is connected to the current measurement circuit.

7. The current sensing circuit suitable for a metal oxide semiconductor field effect transistor circuit as claimed in claim 4, wherein: The current circuit includes a fourth transistor.

8. The current sensing circuit applicable to a metal oxide semiconductor field effect transistor circuit as claimed in claim 7, wherein: The fourth transistor includes an N-type metal oxide semiconductor field effect transistor. The drain of the fourth transistor is connected to the drain of the first transistor. The source of the fourth transistor is connected to the ground. The gate of the fourth transistor is coupled to receive a bias voltage.

9. The current sensing circuit applicable to a metal oxide semiconductor field effect transistor circuit as claimed in claim 4, wherein: The current measurement circuit includes a resistor connected between the drain of the third transistor and ground, and an analog-to-digital converter for converting the voltage across the resistor into a digital signal to obtain the current flowing through the second transistor and the third transistor.

10. The current sensing circuit applicable to a metal oxide semiconductor field effect transistor circuit as claimed in claim 7, wherein: Also includes: The replica second transistor and the replica third transistor are connected in series between a power source and the current circuit. The gates of the replica second transistor and the replica third transistor are connected to the gates of the second transistor and the third transistor respectively.

11. The current sensing circuit applicable to a metal oxide semiconductor field effect transistor circuit according to claim 10, wherein: The replica second transistor includes a P-type metal oxide semiconductor field effect transistor, and the replica third transistor includes a P-type metal oxide semiconductor field effect transistor. The source of the replica second transistor is connected to a power supply, the drain of the replica second transistor is connected to the source of the replica third transistor, and the drain of the replica third transistor is connected to the current circuit.

12. The current sensing circuit applicable to a metal oxide semiconductor field effect transistor circuit according to claim 11, wherein: The current circuit includes a current mirror circuit including a fourth transistor and a diode-connected fifth transistor.

13. The current sensing circuit applicable to a metal oxide semiconductor field effect transistor circuit as claimed in claim 12, wherein: The fourth transistor includes an N-type metal oxide semiconductor field effect transistor, and the fifth transistor includes an N-type metal oxide semiconductor field effect transistor, the drain of the fourth transistor is connected to the drain of the first transistor, the source of the fourth transistor is connected to the ground, and the gate of the fourth transistor is coupled to receive a bias voltage; the drain of the fifth transistor is connected to the drain of the replica third transistor and the gate of the fourth transistor, and the source of the fifth transistor is connected to the ground.

14. The current sensing circuit applicable to a metal oxide semiconductor field effect transistor circuit as claimed in claim 10, wherein: The current measuring circuit includes a resistor connected between the drain of the third transistor and the ground.

15. The current sensing circuit applicable to a metal oxide semiconductor field effect transistor circuit as claimed in claim 1, wherein: The output driver transistor includes an N-type metal oxide semiconductor field effect transistor, the first transistor includes an N-type metal oxide semiconductor field effect transistor, the second transistor includes an N-type metal oxide semiconductor field effect transistor, and the third transistor includes an N-type metal oxide semiconductor field effect transistor.

16. The current sensing circuit applicable to a metal oxide semiconductor field effect transistor circuit as claimed in claim 15, wherein: The device further includes a DC-to-DC converter coupled to the first transistor, the second transistor, and the third transistor.

17. The current sensing circuit applicable to a metal oxide semiconductor field effect transistor circuit as claimed in claim 16, wherein: The DC-to-DC converter comprises: an inductor connected in series with the output driver transistor between a power supply and a ground, wherein a connection node between the inductor and the output driver transistor is connected to the drain of the first transistor, and a gate of the output driver transistor is connected to the gate of the second transistor; a Zener diode having an anode connected to the connection node; at least one capacitor connected between the cathode of the Zener diode and ground; and A pulse width modulation controller, serving as the current measurement circuit, for generating a control signal to be provided to the gate of the output drive transistor; The pulse width modulation controller is controlled by the voltage feedback of the cathode of the Zener diode and the current feedback of the source of the third transistor.

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