Light emitting diode driver and current driver for photoplethysmography

Abstract

The present invention relates to a light emitting diode driver and a current driver for photoplethysmography. The light emitting diode driver comprises an operational amplifier (OP), N current driving circuits and a resistor circuit. The OP compares a reference voltage and a feedback voltage to generate a control voltage. Each of the N current driving circuits is coupled to an LED current path and comprises: an NMOS transistor, which is turned on according to the control voltage in an enabled mode and turned off according to a voltage of a ground terminal in a disabled mode, a drain of the NMOS transistor is coupled to the LED current path, a voltage of a source of the NMOS transistor is the feedback voltage; and a switch circuit, which is coupled to the OP and a gate of the NMOS transistor in the enabled mode to turn on the NMOS transistor, and coupled to the ground terminal and the gate of the NMOS transistor in the disabled mode to turn off the NMOS transistor. The resistor circuit is coupled between the source and the ground terminal, and determines a total current flowing through the N current driving circuits together with the feedback voltage.

Description

Technical Field

[0001] This invention relates to drivers, and more particularly to light-emitting diode drivers and current drivers for photovolume change mapping. Background Technology

[0002] Photoplethysmography (PPG) involves illuminating skin with a controlled light source (e.g., a light-emitting diode (LED)) and measuring changes in light absorption. It can be used in various applications (e.g., heart rate and blood oxygenation measurements). A PPG electronic device may contain multiple LEDs, each used to irradiate different areas of the skin, and each LED is driven by a dedicated / shared current-driven circuit. However, these LEDs do not necessarily operate simultaneously; therefore, a switch (e.g., a metal-oxide-semiconductor (MOS) transistor) is placed between each LED and its corresponding current-driven circuit, and N switches are placed between N LEDs and their corresponding current-driven circuits. When the switch is on, the LED operates according to a drive current; when the switch is off, no current flows through the LED, and it does not operate.

[0003] As mentioned above, since each LED typically requires a large drive current (e.g., more than 100 mA) to operate, the switch must be able to withstand this large drive current. Therefore, the circuit area of ​​the switch is usually very large, which is not conducive to the miniaturization of the circuit and will lead to increased costs. Summary of the Invention

[0004] One of the objectives of this disclosure is to provide a light-emitting diode (LED) driver and a current driver for photoplethysmography (PPG) that can reduce the use of large-area switches, thereby facilitating circuit miniaturization and cost reduction.

[0005] One embodiment of the LED driver for PPG disclosed herein includes an operation amplifier (OP), N current drive circuits, and a resistor circuit, where N is a positive integer. The operation amplifier includes an OP input, an OP inverting input, and an OP output, wherein the OP input receives a reference voltage, the OP inverting input receives a feedback voltage, and the OP output outputs a control voltage. Each of the N current drive circuits is coupled to an LED via an LED current path; in other words, the N current drive circuits are respectively coupled to N LED current paths to couple to N LEDs. Each of the N current drive circuits is operable in one of an enabled mode and a disabled mode, and includes an N-channel metal-oxide-semiconductor (NMOS) transistor and a switching circuit. The NMOS transistor includes a drain, a source, and a gate. The drain is not coupled to the LED current path via any switch. The source is coupled to the inverting input of the operating circuit (OP) via a feedback node. The gate receives the control voltage in the enable mode and a bias voltage from a bias terminal in the disable mode. The voltage of the feedback node is the feedback voltage. A switching circuit is used to couple the OP output to the gate in the enable mode, allowing the control voltage to control the NMOS transistor. The switching circuit also couples the bias terminal to the gate in the disable mode, disabling the NMOS transistor. A resistor circuit is coupled between the feedback node and a low-voltage terminal, and together with the feedback voltage, determines the total current flowing through the N current drive circuits.

[0006] One embodiment of the current driver disclosed herein includes an OP, N current drive circuits, and a resistor circuit, where N is a positive integer. The OP includes an OP input, an OP inverting input, and an OP output, wherein the OP input receives a reference voltage, the OP inverting input receives a feedback voltage, and the OP output outputs a control voltage. Each of the N current drive circuits is coupled to a driven circuit via a current path; in other words, the N current drive circuits are respectively coupled to N current paths to couple to N driven circuits. Each of the N current drive circuits is operable in one of an enabled mode and a disabled mode, and includes an NMOS transistor and a switching circuit. The NMOS transistor includes a drain, a source, and a gate, wherein the drain is not coupled to the current path via any switch, the source is coupled to the OP inverting input via a feedback node, the gate receives the control voltage in the enabled mode and receives a bias voltage at a bias terminal in the disabled mode, and the voltage of the feedback node is the feedback voltage. The switching circuit is used to couple the OP output terminal to the gate in the enabled mode, so that the control voltage controls the NMOS transistor; the switching circuit is also used to couple the bias terminal to the gate in the disabled mode, so that the bias voltage disables the NMOS transistor. The resistor circuit is coupled between the feedback node and a low voltage terminal, and is used together with the feedback voltage to determine the total current flowing through the N current drive circuits.

[0007] The features, practical operation, and effects of the present invention are described in detail below with reference to the accompanying drawings, and preferred embodiments are described in detail. Attached Figure Description

[0008] Figure 1 An embodiment of a light-emitting diode (LED) driver for photoplethysmography (PPG) of the present disclosure is shown;

[0009] Figure 2 Show Figure 1 An embodiment of a switching circuit; and

[0010] Figure 3 An embodiment of the current driver of this disclosure is shown. Detailed Implementation

[0011] This disclosure proposes a light-emitting diode (LED) driver and a current driver for photoplethysmography (PPG), which can reduce the use of large-area switches, thereby facilitating circuit miniaturization and cost reduction.

[0012] Figure 1An embodiment of the LED driver for PPG disclosed herein is shown. Figure 1 The LED driver 100 for PPG includes an operational amplifier (OP) 110, N current drive circuits 120, and a resistor circuit 130, where N is a positive integer (e.g., 1 ≤ N ≤ 5). These circuits are described in the following paragraphs.

[0013] like Figure 1 As shown, the OP 110 includes an OP input terminal (such as...). Figure 1 (as shown by the symbol "+"), an OP inverting input terminal (such as...) Figure 1 The symbol "-" is shown as an OP input terminal. This OP input terminal is used to receive a reference voltage V. REF The reference voltage V REF This can be determined based on implementation requirements. The inverting input of the OP is used to receive a feedback voltage V. FB The feedback voltage V FB Based on the characteristics of this OP110, it will approach the reference voltage V. REF The output of this OP is used to output a control voltage V. CTRL The control voltage V CTRL This is used to control the operation of the N current drive circuits 120. Furthermore, the OP 110 receives a supply voltage V. DD To operate, the supply voltage V DD It depends on the implementation requirements.

[0014] like Figure 1 As shown, each of the N current drive circuits 120 is coupled to an LED current path, and via that LED current path, is coupled to an LED 10; in other words, the N current drive circuits 120 are respectively coupled to N LED current paths to couple to N LEDs 10. Furthermore, the components (e.g., wires, traces, pads, or pins) on each LED current path are determined according to implementation requirements; each LED 10 receives a supply voltage V. DD1 The supply voltage V DD1 It also depends on the implementation requirements and may be the same as or different from the aforementioned supply voltage V. DD In this embodiment, no switch (e.g., a switch capable of handling 100 mA) is required between the N current drive circuits 120 and the N LEDs 10, thus reducing the circuit area required.

[0015] about Figure 1In this embodiment, each of the N current drive circuits 120 is operable in one of an enabled mode and a disabled mode. When any current drive circuit 120 operates in the enabled mode, it transmits current; when any current drive circuit 120 operates in the disabled mode, although it is still electrically connected to the LED 10 via the LED current path, it does not transmit any current.

[0016] like Figure 1 As shown, each of the N current drive circuits 120 includes an N-channel metal-oxide-semiconductor (NMOS) transistor 122 and a switching circuit 124. The NMOS transistor 122 includes a drain, a source, and a gate, wherein the drain is not coupled to the LED current path via any switch, and the source is connected to a feedback node ND. FB Coupled to the inverting input of the OP, the gate is used to receive the aforementioned control voltage V in this enable mode. CTRL And a bias voltage V that receives a bias terminal (e.g., a ground terminal) in this disabled mode. BIAS (For example: a ground voltage), the feedback node ND FB The voltage is the aforementioned feedback voltage V. FB The switching circuit 124 is used to couple the OP output terminal to the gate in this enabled mode, so that the control voltage V... CTRL The NMOS transistor 122 is controlled; the switching circuit 124 is also coupled to the bias terminal and the gate in the disabled mode so that the bias voltage V BIAS The NMOS transistor 122 is disabled. It is worth noting that when the switching circuit 124 is coupled between the OP output and the NMOS transistor 122, the current between the OP output and the NMOS transistor 122 (e.g., a current less than one milliampere, which is equivalent to several microamperes) is very small. Therefore, the switching circuit 124 requires only a small circuit area to handle this current. For example, if the circuit area capable of handling a maximum of 100 milliamperes is A... SW_100 The circuit area A that can withstand a maximum switching current of 1 milliamp. SW_1 Approximately A SW_100 One percent.

[0017] Figure 2 Show Figure 1 An embodiment of the switching circuit 124. For example... Figure 2As shown, the switching circuit 124 includes a first switch 210 and a second switch 220. The first switch 210 is used to couple the OP output terminal to the gate in the enabled mode according to a first switch signal SW1, and to turn off in the disabled mode according to the first switch signal SW1. The second switch 220 is used to turn off in the enabled mode according to a second switch signal SW2, and to couple the bias terminal to the gate in the disabled mode according to the second switch signal SW2. The implementation of the first switch signal SW1 and the second switch signal SW2 can be achieved using known / self-developed techniques. When the NMOS transistor 122 has an NMOS circuit area A... NMOS When capable of withstanding a maximum LED current (e.g., 100 mA), each of the first switch 210 and the second switch 220 has a switching circuit area A. SW It can withstand a maximum switching current (e.g., 1 mA), and the NMOS circuit area A NMOS Greater than the area A of the switching circuit SW (For example: A) NMOS ≥100A SW However, this is not a limitation of the present invention. Where feasible, other known / self-developed switching circuits may be used to replace it. Figure 2 The switching circuit 124.

[0018] like Figure 1 As shown, the resistor circuit 130 is coupled to the feedback node ND. FB Between a low voltage terminal (e.g., a ground terminal) and the feedback voltage V FB Together they determine the total current I flowing through the N current drive circuits 120 TOTAL For example, the total current I TOTAL Equal to the feedback voltage V FB Divide by the total resistance value R of the resistor circuit 130 TOTAL (that is: It is worth noting that when N is greater than one, any two current drive circuits 120 are identical / similar, M of the N current drive circuits 120 operate in the enabled mode, and (NM) of the N current drive circuits 120 operate in the disabled mode, the transmission current of each current drive circuit 120 operating in the enabled mode is between 0 and 1. TOTAL The value of M depends on how much current flows through each current drive circuit 120 (e.g., the current drive circuit 120 without an LED has a current of 0), where M is a positive integer not greater than N. It is also worth noting the total resistance value R of the resistor circuit 130. TOTALIt can be fixed or adjustable, depending on the implementation requirements; the implementation of fixed / adjustable resistors can be achieved using known / self-developed technologies.

[0019] Figure 3 An embodiment of the current driver of this disclosure is shown. Figure 3 The current driver 300 includes an OP 310, N current drive circuits 320, and a resistor circuit 330, where N is a positive integer. The OP 310 includes an OP input terminal (e.g., ...). Figure 3 (as shown by the symbol "+"), an OP inverting input terminal (such as...) Figure 3 (as indicated by the symbol "-") and an OP output terminal, wherein the OP input terminal is used to receive a reference voltage V. REF The inverting input of the OP is used to receive a feedback voltage V. FB The output of this OP is used to output a control voltage V. CTRL Each of the N current drive circuits 320 is coupled to a driven circuit (not shown) via a current path; in other words, the N current drive circuits 320 are coupled to N current paths to couple to N driven circuits (not shown). Each of the N current drive circuits 320 is operable in one of a single-enabled mode and a disabled mode, and includes an NMOS transistor 322 and a switching circuit 324. The NMOS transistor 322 includes a drain, a source, and a gate, wherein the drain is not coupled to the current path via any switch, and the source is coupled to a feedback node ND. FB Coupled to the inverting input of the OP, the gate is used to receive the control voltage V in this enable mode. CTRL and a bias voltage V that receives a bias terminal (e.g., a ground terminal) in this disabled mode. BIAS (For example: a ground voltage), the feedback node ND FB The voltage is the feedback voltage V. FB The switching circuit 324 is used to couple the OP output terminal to the gate in this enabled mode, so that the control voltage V... CTRL The NMOS transistor 322 is controlled; the switching circuit 324 also couples the bias terminal to the gate in the disabled mode, so that the bias voltage V BIAS The NMOS transistor 322 is disabled. The resistor circuit 330 is coupled to the feedback node ND. FB Between a low voltage terminal (e.g., a ground terminal) and the feedback voltage V FB Together they determine the total current I flowing through the N current drive circuits 320 TOTAL . Figure 3 The current driver 300 can be used in applications other than PPG.

[0020] Because those skilled in the art can refer to this Figures 1 to 2 To understand from the disclosure of embodiments Figure 3 Details and variations of the embodiments, as well as repetitive and redundant descriptions, are omitted here.

[0021] Please note that, where feasible, those skilled in the art may selectively implement some or all of the technical features in any of the foregoing embodiments, or selectively implement a combination of some or all of the technical features in the foregoing multiple embodiments, to flexibly implement the present invention.

[0022] In summary, the LED driver and current driver for PPG disclosed herein can reduce the use of large-area switches, thereby facilitating circuit miniaturization and cost reduction.

[0023] While the embodiments of the present invention have been described above, these embodiments are not intended to limit the present invention. Those skilled in the art can make changes to the technical features of the present invention based on the explicit or implicit content of the present invention. All such changes may fall within the scope of patent protection sought by the present invention. In other words, the scope of patent protection of the present invention shall be determined by the scope of the patent application in this specification.

[0024] [Symbol Explanation]

[0025] 100: LED driver for PPG

[0026] 110: Operational Amplifier (OP)

[0027] 120: Current-driven circuit

[0028] 122: NMOS transistor

[0029] 124: Switching Circuit

[0030] 130: Resistor Circuit

[0031] ND FB Feedback Node

[0032] V REF Reference voltage

[0033] V FB Feedback voltage

[0034] V CTRL Control voltage

[0035] V BIAS :bias

[0036] V DD Supply voltage

[0037] V DD1 Supply voltage

[0038] I TOTAL Current

[0039] 10: Light Emitting Diode (LED)

[0040] 210: First Switch

[0041] 220: Second switch

[0042] SW1: First switch signal

[0043] SW2: Second switch signal

[0044] 300: Current Driver

[0045] 310: Operational Amplifier (OP)

[0046] 320: Current drive circuit

[0047] 322: NMOS transistor

[0048] 324: Switching Circuit

[0049] 330: Resistor circuit.

Claims

1. A light-emitting diode driver for photovolume change mapping, comprising: An operational amplifier includes an operational amplifier input terminal, an operational amplifier inverting input terminal, and an operational amplifier output terminal, wherein the operational amplifier input terminal is used to receive a reference voltage, the operational amplifier inverting input terminal is used to receive a feedback voltage, and the operational amplifier output terminal is used to output a control voltage. There are N current-driven circuits, where N is a positive integer. Each of the N current-driven circuits is coupled to a light-emitting diode (LED) current path. Each of the N current-driven circuits is coupled to N LED current paths. Each of the N current-driven circuits can operate in one of an enabled mode and a disabled mode, and includes: An N-channel metal-oxide-semiconductor transistor includes a drain, a source, and a gate, wherein the drain is not coupled to the current path of the light-emitting diode via any switch, the source is coupled to the inverting input of the operational amplifier via a feedback node, the gate is used to receive the control voltage in the enabled mode and to receive a bias voltage at a bias terminal in the disabled mode, and the voltage of the feedback node is the feedback voltage. as well as A switching circuit is used to couple the output of the operational amplifier to the gate in the enabled mode so that the control voltage controls the N-channel metal-oxide-semiconductor transistor. The switching circuit is also used to couple the bias terminal to the gate in the disabled mode so that the bias voltage disables the N-channel metal-oxide-semiconductor transistor. as well as A resistor circuit, coupled between the feedback node and a low-voltage terminal, is used to determine the total current flowing through the N current drive circuits together with the feedback voltage.

2. The LED driver for the photoplethysmography method according to claim 1, wherein in the disabled mode, the N-channel metal-oxide-semiconductor transistor is turned off, while the drain of the N-channel metal-oxide-semiconductor transistor is still electrically connected to an LED via the LED current path.

3. The light-emitting diode driver for the optical volume change mapping method according to claim 1, wherein N is greater than one, a portion of the N current driving circuits operates in the enabled mode, and the other portions of the N current driving circuits operate in the disabled mode.

4. The light-emitting diode driver for photovolume change mapping according to claim 1, wherein the N-channel metal-oxide-semiconductor transistor has an N-channel metal-oxide-semiconductor circuit area capable of withstanding a maximum N-channel metal-oxide-semiconductor current; the switching circuit includes a first switch and a second switch, the first switch being used to couple the output terminal of the operational amplifier to the gate in the enabled mode, the second switch being used to couple the bias terminal to the gate in the disabled mode, each of the first switch and the second switch having a switching circuit area capable of withstanding a maximum switching current; and the N-channel metal-oxide-semiconductor circuit area being larger than the switching circuit area.

5. The light-emitting diode driver for the optical volume change tracing method according to claim 1, wherein both the bias terminal and the low-voltage terminal are grounded terminals.

6. The LED driver for the optical volume change mapping method according to claim 1, wherein the total resistance value of the resistive circuit is adjustable.

7. A current driver, comprising: An operational amplifier includes an operational amplifier input terminal, an operational amplifier inverting input terminal, and an operational amplifier output terminal, wherein the operational amplifier input terminal is used to receive a reference voltage, the operational amplifier inverting input terminal is used to receive a feedback voltage, and the operational amplifier output terminal is used to output a control voltage. There are N current-driven circuits, where N is a positive integer. Each of the N current-driven circuits is coupled to a current path. Each of the N current-driven circuits is coupled to N current paths respectively. Each of the N current-driven circuits can operate in either a single-enabled mode or a disabled mode. Each of the N current-driven circuits includes: An N-channel metal-oxide-semiconductor transistor includes a drain, a source, and a gate, wherein the drain is not coupled to the current path via any switch, the source is coupled to the inverting input of the operational amplifier via a feedback node, the gate is used to receive the control voltage in the enabled mode and to receive a bias voltage at a bias terminal in the disabled mode, and the voltage of the feedback node is the feedback voltage. as well as A switching circuit is used to couple the output of the operational amplifier to the gate in the enabled mode so that the control voltage controls the N-channel metal-oxide-semiconductor transistor. The switching circuit is also used to couple the bias terminal to the gate in the disabled mode so that the bias voltage disables the N-channel metal-oxide-semiconductor transistor. as well as A resistor circuit, coupled between the feedback node and a low-voltage terminal, is used to determine the total current flowing through the N current drive circuits together with the feedback voltage.

8. The current driver of claim 7, wherein in the disabled mode, the N-channel metal-oxide-semiconductor transistor is turned off, while the drain of the N-channel metal-oxide-semiconductor transistor is still electrically connected to a driven circuit via the current path.

9. The current driver of claim 7, wherein N is greater than one, a portion of the N current drive circuits operates in the enabled mode, and other portions of the N current drive circuits operate in the disabled mode.

10. The current driver of claim 7, wherein the N-channel metal-oxide-semiconductor transistor has an N-channel metal-oxide-semiconductor circuit area capable of withstanding a maximum N-channel metal-oxide-semiconductor current; the switching circuit includes a first switch and a second switch, the first switch being configured to couple the output of the operational amplifier to the gate in the enabled mode, the second switch being configured to couple the bias terminal to the gate in the disabled mode, each of the first switch and the second switch having a switching circuit area capable of withstanding a maximum switching current; and the N-channel metal-oxide-semiconductor circuit area being larger than the switching circuit area.

Images