High-side switching circuit

Abstract

The invention relates to a high-side switching circuit. A circuit includes an input terminal (VBB), an output terminal (VOUT), a first transistor (102), a second transistor (106), a charge pump circuit (118), a resistor (104), and a current source (112). The input terminal (VBB) is configured to provide an input voltage. The output terminal (VOUT) is configured to provide an output voltage. The first transistor (102) has a first terminal coupled to the input terminal (VBB), a second terminal coupled to the output terminal (VOUT), and a control terminal. The charge pump circuit (118) has an output coupled to the control terminal. The resistor (104) has a first terminal coupled to the control terminal, and a second terminal. The second transistor (106) has a first terminal coupled to the second terminal of the resistor (104), a second terminal coupled to the output terminal (VOUT), and a control terminal. The current source (112) has an input coupled to the control terminal of the second transistor (106).

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuitry, and more specifically, to high-side switching circuits. BACKGROUND

[0002] A high-side switch is a switch connected between a power supply and a load circuit to control the power supply to the load circuit. The switching device in a high-side switching circuit can be a relay or a semiconductor switching device, such as a transistor. Semiconductors have many advantages over electromechanical switches in high-side switching applications. For example, semiconductor switches can reduce the risk of electrical sparking, reduce circuit area, and reduce cost relative to electromechanical switches. SUMMARY

[0003] In one example, a circuit includes an input terminal, an output terminal, a first transistor, a second transistor, a charge pump circuit, and a resistor. The input terminal is configured to provide an input voltage. The output terminal is configured to provide an output voltage. The first transistor has a first terminal coupled to the input terminal, a second terminal coupled to the output terminal, and a control terminal. The charge pump circuit has an output coupled to the control terminal. The resistor has a first terminal coupled to the control terminal, and a second terminal. The second transistor has a first terminal coupled to the second terminal of the resistor, a second terminal coupled to the output terminal, and a control terminal. A current source has an input coupled to the control terminal of the second transistor.

[0004] In another example, a circuit includes an input terminal, an output terminal, a first transistor, a second transistor, a resistor, and a control circuit. The first transistor is configured to conduct current from the input terminal to the output terminal. The first transistor has a control terminal. The second transistor and the resistor are coupled in series between the control terminal and the output terminal. The second transistor has a control terminal. The control circuit has an output coupled to the control terminal of the second transistor. The control circuit is configured to turn on the second transistor in response to the current being greater than a threshold value, and turn off the second transistor in response to the current being less than the threshold value.

[0005] In another example, a system includes a power supply, a high-side switching circuit, and a load circuit. The power supply has an output. The high-side switching circuit has a switch input coupled to the output of the power supply, and a switch output. The load circuit has an input coupled to the switch output. The high-side switching circuit includes a first transistor, a second transistor, a charge pump circuit, a resistor, a current source, and a switch. The first transistor has a first terminal coupled to the switch input, a second terminal coupled to the switch output, and a control terminal. The charge pump circuit has an output coupled to the control terminal. The resistor has a first terminal coupled to the control terminal, and a second terminal. The second transistor has a first terminal coupled to the second terminal of the resistor, a second terminal coupled to the output terminal, and a control terminal. The current source has an input. The switch is coupled between the control terminal of the second transistor and an input terminal of the current source. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic diagram of an example high-side switch circuit suitable for low power applications.

[0007] Figure 2 for Figure 1 Figure 2 is a graph of example signals in a high-side switching circuit.

[0008] Figure 3 To include Figure 1 Figure 2 is a block diagram of an example system of a high-side switch circuit. DETAILED DESCRIPTION

[0009] High-side switching circuits can be used to control power supply in a variety of applications. However, their use in low-power applications is limited because they can consume power even when the load current is very low. Figure 1 FIG1 is a schematic diagram of an example high-side switch circuit 100 suitable for use in low-power applications. High-side switch circuit 100 includes transistor 102, resistor 104, transistor 106, resistor 108, transistor 110, current source 112, switch 114, and control circuit 116. Transistor 102 is a pass transistor that conducts current from an input terminal (VBB) to an output terminal (VOUT). VBB can be coupled to a power source such as a battery, and VOUT can be coupled to a load circuit powered by high-side switch circuit 100. Transistor 102 can be an n-channel field-effect transistor (NFET). A first terminal (e.g., drain) of transistor 102 is coupled to VBB. A second terminal (e.g., source) of transistor 102 is coupled to VOUT. A control terminal (e.g., gate) of transistor 102 is coupled to resistor 104 and control circuit 116. Control circuit 116 provides a control signal 124 that turns transistor 102 on or off.

[0010] The resistor 104 and the transistor 106 are coupled in series between the control terminal of the transistor 102 and VOUT to reduce the voltage difference between VOUT and the control terminal of the transistor 102 when the transistor 102 is off. Thus, for example, if a transient voltage is present on VOUT, the connection of VOUT to the control terminal of the transistor 102 can prevent the transistor 102 from turning on erroneously if the transistor 102 is off. However, if the resistor 104 directly connected VOUT to the control terminal of the transistor 102 (e.g., the transistor 106 is not present), the current through the resistor 104 to VOUT would increase the power consumed by the high-side switch circuit 100 and can make the high-side switch circuit 100 less suitable for use in low-power applications. In some implementations of the high-side switch circuit 100, the resistor 104 can have a resistance of about two mega-ohms and the resistor 108 can have a resistance of about 1.25 mega-ohms. In some implementations of the high-side switch circuit 100, the resistors 104 and 108 have different resistance values.

[0011] In the high-side switch circuit 100, the first terminal of the resistor 104 is coupled to the control terminal of the transistor 102. The second terminal of the resistor 104 is coupled to the first terminal (e.g., drain) of the transistor 106. The second terminal (e.g., source) of the transistor 106 is coupled to VOUT. The control terminal (e.g., gate) of the transistor 106 is coupled to the current source 112 via the switch 114. The first terminal of the switch 114 is coupled to the control terminal of the transistor 106. The second terminal of the switch 114 is coupled to the input of the current source 112. The control input of the switch 114 is coupled to the output of the control circuit 116. The output of the current source 112 is coupled to a reference terminal (e.g., ground).

[0012] The control circuit 116 turns on the transistor 106 to connect the control terminal of the transistor 102 to VOUT through the resistor 104 and turns off the transistor 106 to disconnect the control terminal of the transistor 102 from VOUT. If the current flowing through the transistor 102 is greater than a predetermined threshold (e.g., the high-side switch circuit 100 is operating in a normal mode), the control circuit 116 can turn on the transistor 106. If the current flowing through the transistor 102 is less than the threshold (e.g., the high-side switch circuit 100 is operating in a low-power mode), the control circuit 116 can turn off the transistor 106. If the transistor 106 is off, the current flowing from the control circuit 116 to VOUT is significantly reduced, which can make the high-side switch circuit 100 suitable for use in low-power applications.

[0013] The transistor 106 can be a native transistor (e.g., a native NFET). Thus, the threshold voltage of the transistor 106 can be very low (e.g., a negative threshold voltage, a zero volt threshold, etc.) and the transistor 106 can normally be on. If the switch 114 is off, then the voltage at the control terminal of the transistor 106 is set by the resistor 108 and the transistor 110. The series coupled resistor 108 and transistor 110 pull the control terminal of the transistor 106 to VOUT to turn on the transistor 106. The transistor 110 can be a native NFET. A first terminal of the resistor 108 is coupled to the control terminal of the transistor 106. A second terminal of the resistor 108 is coupled to a first terminal (e.g., drain) of the transistor 110. A second terminal (e.g., source) of the transistor 110 is coupled to VOUT. A control terminal (e.g., gate) of the transistor 110 is also coupled to VOUT. The transistor 110 can prevent current from flowing from VOUT to the switch 114. The transistor 110 can not be included in some examples of the high-side switch circuit 100.

[0014] The control circuit 116 provides a switch control signal 126 to control the switch 114. If the current through the transistor 102 is less than a threshold, then the control circuit 116 (via the switch control signal 126) closes the switch 114 to turn off the transistor 106. The control circuit 116 provides the switch control signal 126 at an output of the control circuit 116 that is coupled to a control input of the switch 114. The switch control signal 126 closes the switch 114 to pull the control terminal of the transistor 106 to a voltage that is much lower than the voltage on VOUT, which turns off the transistor 106. For example, the current source 112 can pull the control terminal of the transistor 106 to a voltage that is 2 volts, 2.5 volts, 5 volts, etc., less than the voltage at VOUT.

[0015] The control circuit 116 includes a charge pump circuit 118, a charge pump circuit 120, and a power mode circuit 122. The power mode circuit 122 measures the current flowing through the transistor 102 and controls the switch 114, the charge pump circuit 118, and the charge pump circuit 120 based on the measured current. For example, the power mode circuit 122 can compare the measurement of the current flowing through the transistor 102 to a threshold current. If the current flowing through the transistor 102 is greater than a first threshold current (e.g., 100 milliamps, 150 milliamps), the power mode circuit 122 provides a control signal to enable (activate) the charge pump circuit 118, disable (deactivate) the charge pump circuit 120, and open the switch 114. If the current flowing through the transistor 102 is less than a second threshold current (e.g., 100 milliamps, 150 milliamps) (the high-side switch circuit 100 is in a low-power mode), the power mode circuit 122 provides a first charge pump control signal to disable (deactivate) the charge pump circuit 118, a second charge pump control signal to enable (activate) the charge pump circuit 120, and a switch control signal to close the switch 114. In various implementations of the high-side switch circuit 100, the first and second threshold currents can be the same or different.

[0016] If the current through the transistor 102 is greater than the threshold current, the charge pump circuit 118 provides an output voltage to turn on the transistor 102. If the current through the transistor 102 is less than the threshold current, the charge pump circuit 120 provides an output voltage to turn on the transistor 102. The output voltage provided by the charge pump circuit 118 and the charge pump circuit 120 can be at least the threshold voltage of the transistor 102 greater than the voltage at VOUT. For example, the output voltage provided by the charge pump circuit 118 and the charge pump circuit 120 can be five volts greater than the voltage at VOUT. The charge pump circuit 118 provides sufficient current to turn on the transistor 102, with some of the current flowing through the resistor 104. The charge pump circuit 120 can provide substantially less current than the charge pump circuit 118 because, in the low-power mode, no current flows from the charge pump circuit 120 through the resistor 104 to VOUT. Thus, in operation, the charge pump circuit 120 can consume less power than the charge pump circuit 118, which makes the high-side switch circuit 100 more suitable for use in low-power applications.

[0017] Figure 2 A plot of example signals in the high-side switch circuit 100. Figure 2The gate-to-source voltage of transistor 102 (VGS102), the gate-to-source voltage of transistor 106 (VGS106), and the current in resistor 104 (CURRENT104) are shown. At time 202, control circuit 116 generates control signal 124 to turn on transistor 102, and VGS102 increases from 0 volts to 5 volts. VGS106 is at about zero volts, and transistor 106 is on. As VGS102 increases and transistor 106 is on, the current through resistor 104 increases to about 2.5 milliamps.

[0018] At time 204, control circuit 116 provides control signal 126 to close switch 114. As switch 114 closes, current source 112 draws current from the control terminal of transistor 106, VGS106 drops to about -2.5 volts, and transistor 106 turns off. Turning off transistor 106 causes the current through resistor 104 to decrease to about 55 picoamps.

[0019] At time 206, control circuit 116 provides control signal 126 to open switch 114. As switch 114 opens, VGS106 increases to about zero volts, transistor 106 turns on, and the current through resistor 104 and transistor 106 increases to about 2.5 microamps. Thus, with transistor 106 off, the current through resistor 104 is significantly lower (e.g., more than 4 orders of magnitude lower) than when transistor 106 is on, which makes high-side switch circuit 100 suitable for use in low-power applications.

[0020] Figure 3 A block diagram of an example system 300 that includes high-side switch circuit 100 is shown. System 300 can be provided in a vehicle, industrial equipment, etc. System 300 includes a power source 302, high-side switch circuit 100, and a load circuit 304. In some implementations, power source 302 can be a battery (e.g., a vehicle battery). High-side switch circuit 100 is coupled between power source 302 and load circuit 304 to control the voltage provided to load circuit 304. High-side switch circuit 100 can act as an electronic fuse that can limit or suspend the flow of current to load circuit 304 if the current exceeds a threshold. In vehicle applications, load circuit 304 can be any of a variety of circuits. For example, load circuit 304 can be a vehicle lighting circuit, a vehicle control circuit (e.g., engine control), an advanced driver assistance system, or other vehicle circuit. Because high-side switch circuit 100 can disconnect resistor 104 in situations where the current drawn by load circuit 304 is very low, high-side switch circuit 100 can be used in vehicle applications. For example, high-side switch circuit 100 can be used in applications where a vehicle is turned off (e.g., parked) for a long period of time without depleting the vehicle battery.

[0021] In this specification, the term "coupled" can encompass a connection, communication, or signal path that enables a functional relationship consistent with this specification. For example, if device A produces a signal for controlling device B to perform an action: (a) in a first instance, device A is coupled to device B by a direct connection; or (b) in a second instance, device A is coupled to device B through intermediate component C, such that device B is controlled by device A via a control signal produced by device A, if intermediate component C does not alter the functional relationship between device A and device B.

[0022] As used herein, the terms "terminal," "node," "interconnect," "pin," and "lead" are used interchangeably. Unless expressly stated to the contrary, these terms are generally used to denote an interconnect or their terminations between device elements, circuit elements, integrated circuits, devices, or other electronic or semiconductor components.

[0023] Circuits or devices described herein as including certain components can instead be adapted to be coupled to those components to form the described circuitry or devices. For example, structures described as including one or more semiconductor elements (e.g., transistors), one or more passive elements (e.g., resistors, capacitors, and / or inductors), and / or one or more sources (e.g., voltage and / or current sources) can instead include only the semiconductor elements within a single physical device (e.g., a semiconductor die and / or an integrated circuit (IC) package) and can be adapted to be coupled to at least some of the passive elements and / or sources to form the described structures, e.g., when manufactured by an end user and / or third party or after manufacture.

[0024] While specific transistor usage is described herein, other transistors (or equivalent devices) can be used instead with little or no change to the remaining circuitry. For example, field effect transistors ("FETs") (e.g., n-channel FETs (NFETs) (n-type transistors) or p-channel FETs (PFETs) (p-type transistors)), bipolar junction transistors (BJTs) (e.g., NPN transistors or PNP transistors), insulated gate bipolar junction transistors (IGBTs), and / or junction field effect transistors (JFETs) can be used instead of or in combination with the devices described herein. The transistors can be depletion mode devices, drain extended devices, enhancement mode devices, native transistors, or other types of device structure transistors. Furthermore, the devices can be implemented in / on silicon substrates (Si), silicon carbide substrates (SiC), gallium nitride substrates (GaN), or gallium arsenide substrates (GaAs).

[0025] In the claims, reference can be made to a transistor's control input and its current terminals. In the context of a FET, the control input (or transistor control terminal) is the gate, and the current terminals are the drain and source. In the context of a BJT, the control input is the base, and the current terminals are the collector and emitter.

[0026] Reference herein to a FET being "on" means that a conductive channel of the FET exists and drain current can flow through the FET. Reference herein to a FET being "off" means that a conductive channel does not exist, and thus drain current does not flow through the FET. However, an "off" FET can have current flow through the body diode of the transistor.

[0027] The circuits described herein can be reconfigurable to include additional or different components to provide at least some similar functionality to that available prior to the component replacement. Unless otherwise noted, components shown as resistors generally represent any one or more elements coupled in series and / or parallel to provide the amount of impedance represented by the shown resistor. For example, a resistor or capacitor shown and described herein as a single component can actually be a plurality of resistors or capacitors respectively coupled in parallel between the same nodes. For example, a resistor or capacitor shown and described herein as a single component can actually be a plurality of resistors or capacitors respectively coupled in series between the same two nodes as the single resistor or capacitor.

[0028] While certain elements of the described examples are included in an integrated circuit and other elements are external to the integrated circuit, in other example embodiments additional or fewer features can be incorporated into the integrated circuit. In addition, some or all of the features shown as external to the integrated circuit can be included in the integrated circuit, and / or some features shown as internal to the integrated circuit can be incorporated external to the integrated circuit. As used herein, the term "integrated circuit" refers to one or more circuits that are (i) incorporated in a semiconductor substrate above / below the semiconductor substrate; (ii) incorporated in a single semiconductor package; (iii) incorporated in the same module; and / or (iv) incorporated on / on the same printed circuit board.

[0029] In the foregoing description, use of the phrase "ground" includes chassis ground, ground plane, floating ground, virtual ground, digital ground, common ground, and / or any other form of ground connection as can be suitable for use with the teachings of the present specification. In the present specification, "about," "approximately," or "substantially" before a parameter means within + / - 10% of the parameter, or if the parameter is zero, a reasonable range of values about zero, unless otherwise stated.

[0030] In the described embodiments, modifications are possible and other embodiments are possible within the scope of the claims.

Claims

1. A circuit, comprising: an input terminal configured to provide an input voltage; an output terminal configured to provide an output voltage; a first transistor having a first terminal coupled to the input terminal, a second terminal coupled to the output terminal, and a control terminal; a charge pump circuit having an output coupled to the control terminal; and a resistor having a first terminal coupled to the control terminal, and a second terminal; a second transistor having a first terminal coupled to the second terminal of the resistor, a second terminal coupled to the output terminal, and a control terminal; and a current source having an input coupled to the control terminal of the second transistor.

2. The circuit of claim 1, wherein the second transistor is a native transistor.

3. The circuit of claim 1, further comprising a third transistor having a first terminal coupled to the control terminal of the second transistor, a second terminal coupled to the second terminal of the second transistor, and a control terminal coupled to the second terminal of the third transistor.

4. The circuit of claim 3, further comprising a second resistor coupled between the control terminal of the second transistor and the first terminal of the third transistor.

5. The circuit of claim 3, wherein the third transistor is a native transistor.

6. The circuit of claim 1, further comprising a switch coupled between the input of the current source and a control terminal of the second transistor.

7. The circuit of claim 6, wherein: the charge pump circuit is a first charge pump circuit; and the circuit includes a second charge pump circuit having an output coupled to the control terminal of the first transistor.

8. The circuit of claim 7, further comprising a control circuit having a first output coupled to the first charge pump circuit, a second output coupled to a control input of the switch, and a third output coupled to the second charge pump circuit, the control circuit configured to: provide a first charge pump control signal at the first output, the first charge pump control signal having a first state to enable the first charge pump circuit to cause the circuit to operate in a first mode; provide a switch control signal at the second output, the switch control signal having a second state to open the switch to cause the circuit to operate in the first mode; provide a second charge pump control signal at the third output, the second charge pump control signal having a second state to disable the second charge pump circuit to cause the circuit to operate in the first mode; provide the first charge pump control signal at the first output, the first charge pump control signal having the second state to disable the first charge pump circuit to cause the circuit to operate in a second mode; providing the switch control signal at the second output, the switch control signal having the first state to close the switch to operate the circuit in the second mode; and providing the second charge pump control signal at the third output, the second charge pump control signal having the first state to enable the second charge pump circuit to operate the circuit in the second mode.

9. A circuit, comprising: an input terminal and an output terminal; a first transistor configured to conduct current from the input terminal to the output terminal, the first transistor having a control terminal; a second transistor and a resistor coupled in series between the control terminal and the output terminal, the second transistor having a control terminal; a control circuit having an output coupled to the control terminal of the second transistor, the control circuit configured to: turn on the second transistor in response to the current being greater than a threshold; and turn off the second transistor in response to the current being less than the threshold.

10. The circuit of claim 9, further comprising a current source having an input coupled to the control terminal of the second transistor, the current source configured to provide a voltage at the control terminal of the second transistor that is less than a voltage at the output terminal.

11. The circuit of claim 10, further comprising a switch coupled between the input of the current source and the control terminal of the second transistor, the switch having a control input coupled to the output of the control circuit; and the switch configured to pass current from the control terminal of the second transistor in response to the current being less than the threshold.

12. The circuit of claim 9, wherein the second transistor is a native transistor.

13. The circuit of claim 9, further comprising a third transistor coupled between the control terminal of the second transistor and the output terminal, the third transistor having a control terminal coupled to the output terminal.

14. The circuit of claim 13, further comprising a resistor coupled between the control terminal of the second transistor and the third transistor.

15. The circuit of claim 13, wherein the third transistor is a native transistor.

16. The circuit of claim 9, wherein the control circuit includes: a first charge pump circuit having an output coupled to the control terminal of the first transistor, the first charge pump circuit configured to provide a control signal in response to the current being greater than the threshold; and a second charge pump circuit having an output coupled to the control terminal of the first transistor, the second charge pump circuit configured to provide the control signal in response to the current being less than the threshold.

17. A system, comprising: a power supply having an output; a high-side switch circuit having a switch input coupled to the output of the power supply, and a switch output; and a load circuit having an input coupled to the switch output; wherein the high-side switch circuit includes: a first transistor having a first terminal coupled to the switch input, a second terminal coupled to the switch output, and a control terminal; a charge pump circuit having an output coupled to the control terminal; and a resistor having a first terminal coupled to the control terminal, and a second terminal; a second transistor having a first terminal coupled to the second terminal of the resistor, a second terminal coupled to the switch output, and a control terminal; a current source having an input; and a switch coupled between the control terminal of the second transistor and the input of the current source.

18. The system of claim 17, wherein the resistor is a first resistor; and the high-side switch circuit includes: a third transistor having a first terminal, a second terminal coupled to the second terminal of the second transistor, and a control terminal coupled to the second terminal of the third transistor; and a second resistor coupled between the control terminal of the second resistor and the first terminal of the third transistor.

19. The system of claim 18, wherein the second transistor and the third transistor are native transistors.

20. The system of claim 17, wherein: the charge pump circuit is a first charge pump circuit; and the high-side switch circuit includes: a second charge pump circuit; and a control circuit configured to: activate the first charge pump circuit in response to a current flowing through the first transistor being greater than a threshold value; and activate the second charge pump circuit in response to a current flowing through the first transistor being less than the threshold value.

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