Light emitting device driving circuit, PPG sensor and electronic device

Abstract

The embodiment of the present application provides a light-emitting device driving circuit, a PPG sensor and an electronic device, relates to the field of electronic devices, and improves the power supply efficiency of a light source. The light-emitting device driving circuit comprises a voltage conversion circuit, at least one light-emitting device, a current driving circuit and a controller; any light-emitting device and the current driving circuit are connected in series between the output end and the ground end of the voltage conversion circuit; the controller is configured to output a first control signal to the current driving circuit; the current driving circuit is configured to provide a predetermined current to the first light-emitting device according to the first control signal; the controller is configured to output a second control signal to the voltage conversion circuit according to the electrical parameter on the path of the first light-emitting device and the current driving circuit; and the voltage conversion circuit is configured to adjust the voltage of the output end of the voltage conversion circuit according to the second control signal.

Description

Technical Field

[0001] The present application relates to the field of electronic equipment, and in particular to a light-emitting device driving circuit, a photoplethysmography (PPG) sensor, and electronic equipment. Background Art

[0002] At present, light-emitting devices such as laser diodes (LD) or light-emitting diodes (LED) are widely used in electronic devices. Generally, light-emitting devices are mainly used in electronic devices for display backlight, measurement (for example, distance, biological characteristics of the human body, etc.), signal indication, lighting and other functions. For example, a photoplethysmograph (PPG) sensor mainly drives a light-emitting device to emit a test light signal. Part of the test light signal will be reflected inside the skin or at the skin interface; part of the test light signal will be scattered inside the skin, and part of the scattered light signal will return to the PPG sensor and be received by the detector of the PPG sensor. This part of the scattered signal is called the backscattered signal. In addition to receiving part of the scattered signal, the detector will also receive part of the reflected signal. Through the backscattered signal or the reflected signal, the human body can be continuously measured to collect data such as heart rate and blood oxygen.

[0003] Currently, PPG sensors consume relatively high power (approximately 40% of the total power consumption in wristbands and approximately 15% in watches). This requires further increasing the driving current of the light-emitting device, particularly for deep skin testing. This high power consumption prevents some wearable products from using features such as real-time heart rate monitoring and continuous blood oxygen monitoring. In the future, more health features will need to be integrated with PPG sensors, and real-time heart rate monitoring and continuous blood oxygen monitoring will be essential. Therefore, it is necessary to reduce the power consumption of PPG sensors. In PPG sensors, the light-emitting device accounts for a significant portion of the power consumption, and reducing this power consumption can significantly reduce the power consumption of the PPG sensor. Therefore, improving the power supply efficiency of the light-emitting device is key to reducing overall power consumption. Summary of the Invention

[0004] Embodiments of the present application provide a light-emitting device driving circuit, a photoplethysmography (PPG) sensor, and an electronic device to improve the power supply efficiency of the light-emitting device.

[0005] To achieve the above objectives, this application adopts the following technical solutions:

[0006] In a first aspect, a light-emitting device driving circuit is provided. The light-emitting device driving circuit includes: a voltage conversion circuit, at least one light-emitting device, a current driving circuit, and a controller; each light-emitting device and the current driving circuit are connected in series between an output terminal of the voltage conversion circuit and a ground terminal. The controller is configured to output a first control signal to the current driving circuit; the current driving circuit is configured to provide a predetermined current to the first light-emitting device based on the first control signal; the controller is configured to output a second control signal to the voltage conversion circuit based on electrical parameters of a path between the first light-emitting device and the current driving circuit; and the voltage conversion circuit is configured to adjust a voltage at an output terminal of the voltage conversion circuit based on the second control signal. Thus, when the controller controls the current driving circuit to output a predetermined current to a first light-emitting device among the at least one light-emitting device using the first control signal, the controller can output a second control signal to the voltage conversion circuit based on the electrical parameters of the path between the first light-emitting device and the current driving circuit. The voltage conversion circuit can then adjust the voltage at the output terminal in real time based on the second control signal, rather than operating at a maximum fixed voltage to supply power to all light-emitting devices in a scenario that satisfies the light-emitting device's limit (maximum current), thereby improving the power supply efficiency of the light-emitting devices and reducing overall power consumption.

[0007] In one possible implementation, a current driving circuit includes a current source and a switching circuit; a common terminal of the switching circuit is coupled to the current source, and any light-emitting device is coupled to any selected terminal of the switching circuit; a first control signal includes a switch control signal and a current control signal; the switching circuit is configured to, in accordance with the switch control signal, conduct electricity to the selected terminal coupled to the common terminal of the first light-emitting device, thereby coupling the current source to the first light-emitting device; wherein the switch control signal is synchronized with a lighting timing of the first light-emitting device, i.e., when the switch control signal controls the current source to couple to the first light-emitting device, the first light-emitting device is illuminated; and the current source is configured to provide a predetermined current to the first light-emitting device in accordance with the current control signal. Furthermore, the first control signal and the second control signal corresponding to the same first light-emitting device need to be synchronized. For example, the second control signal controls the voltage conversion circuit only when the first control signal controls the current driving circuit to drive the first light-emitting device to light, or before or after the first control signal controls the current driving circuit to drive the first light-emitting device to light, and the advance or delay (delay) time can be arbitrarily configured.

[0008] In one possible implementation, the electrical parameter includes a voltage drop across the current drive circuit; the controller is configured to detect the voltage drop across the current drive circuit and output a second control signal to the voltage conversion circuit based on the voltage drop; when the voltage drop is greater than a set threshold, the second control signal controls the voltage conversion circuit to reduce the voltage at the output; and when the voltage drop is less than the set threshold, the second control signal controls the voltage conversion circuit to increase the voltage at the output. In this possible implementation, the voltage drop or voltage margin (headroom voltage) of the current source can be utilized to achieve automatic voltage regulation in the voltage conversion circuit.

[0009] In one possible implementation, the electrical parameter includes the driving current of the first light-emitting device; the controller is configured to output a second control signal to the voltage conversion circuit according to the driving current of the first light-emitting device. In this possible implementation, the driving current of the first light-emitting device can be used to achieve automatic voltage regulation of the voltage conversion circuit. For example, if the current of the current source increases or the driving current of the first light-emitting device (of course, in a series circuit, the current of the current source is equal to the driving current of the first light-emitting device), the output voltage of the voltage conversion circuit is increased; if the current of the current source increases or the driving current of the first light-emitting device decreases, the output voltage of the voltage conversion circuit is decreased. In this way, the voltage drop of the additional current source or the headroom voltage is reduced, thereby reducing the power consumption of the system.

[0010] In one possible implementation, the controller is specifically configured to query the expected voltage value corresponding to the driving current of the first light-emitting device according to a lookup table, and output a second control signal to the voltage conversion circuit according to the expected voltage value, and the second control signal is used to control the voltage conversion circuit to output the expected voltage value at the output end.

[0011] In one possible implementation, the controller is specifically configured to calculate the expected voltage value corresponding to the driving current of the first light-emitting device according to a set formula, and output a second control signal to the voltage conversion circuit according to the expected voltage value, and the second control signal is used to control the voltage conversion circuit to output the expected voltage value at the output end.

[0012] In one possible implementation, the controller is further configured to sequentially output the first control signal corresponding to each light-emitting device to the current driving circuit based on the voltages at the output terminals of the voltage conversion circuit corresponding to the at least two light-emitting devices, in descending order or ascending order. In this way, the capacitor at the output terminal of the voltage conversion circuit is in a continuously charging or discharging state, thereby avoiding losses caused by alternating charging and discharging of the capacitor during a PRF cycle.

[0013] In a possible implementation, the voltage conversion circuit includes at least any one of the following: a boost circuit and a buck-boost circuit.

[0014] In a second aspect, a light-emitting device driving circuit is provided. The light-emitting device driving circuit includes: a voltage conversion circuit, at least one light-emitting device, a current driving circuit, and a controller. The voltage conversion circuit includes a feedback terminal and an output terminal, wherein a first resistor and a second resistor are connected in series between the output terminal and a ground terminal; the connection point of the first resistor and the second resistor is coupled to the feedback terminal; a first light-emitting device is connected in series between the output terminal and the current driving circuit, and a third resistor is coupled between the connection point of the first light-emitting device and the current driving circuit and the feedback terminal; the controller is configured to output a first control signal to the current driving circuit; the current driving circuit is configured to provide a predetermined current to the first light-emitting device based on the first control signal; the voltage conversion circuit is configured to control the output terminal to decrease the voltage when a first voltage at the feedback terminal is determined to be higher than a predetermined voltage value; or to control the output terminal to increase the voltage when a second voltage at the feedback terminal is determined to be lower than a predetermined voltage value. The operating principle of the voltage conversion circuit is that when the voltage at the feedback terminal FB is greater than a predetermined voltage value Vref, the voltage conversion circuit decreases the output voltage of Vout; when the voltage at the feedback terminal FB is less than the predetermined voltage value Vref, the voltage conversion circuit increases the output voltage of the output terminal Vout. Through this feedback control, the voltage at the feedback terminal FB is ultimately stabilized at Vref. That is, the voltage at the output terminal Vout of the voltage conversion circuit is stabilized at Vref*(R1+R2) / R2, where R1 is the first resistor and R2 is the second resistor. In this way, a resistor can be connected from one end of each light-emitting device (the cathode of the LED) to the feedback terminal FB of the voltage conversion circuit 71 to automatically control the voltage at the output terminal Vout of the voltage conversion circuit 71. In this way, a resistor can be connected from one end of each light-emitting device (the cathode of the LED) to the feedback terminal FB of the voltage conversion circuit to automatically control the voltage at the output terminal Vout of the voltage conversion circuit. The specific process is as follows (assuming that the drive current of each light-emitting device is fixed): After the voltage conversion circuit is activated, when no current flows through the light-emitting device, the output voltage Vout is Vref*(R1+R2) / R2 (actual LEDs may have a small current flowing through them, causing the output voltage to vary, but this does not affect the process analysis). After the current drive circuit is activated and outputs a predetermined current, a voltage flows through the selected first light-emitting device, forming a voltage drop in the current drive circuit. As the voltage drop across the current drive circuit increases, the voltage at the feedback terminal FB increases. When the first voltage at the feedback terminal FB exceeds a predetermined voltage, the voltage conversion circuit reduces the output voltage Vout. As the voltage at the output Vout of the voltage conversion circuit decreases, the voltage drop across the first light-emitting device remains unchanged, which in turn reduces the voltage drop across the current drive circuit, causing the voltage at the feedback terminal FB to decrease. Ultimately, the voltage at the feedback terminal FB remains at the critical level of Vref. Ultimately, the voltage at the output terminal Vout of the voltage conversion circuit is Vout = Vref * [1 / Rx + 1 / R2 + 1 / R1] * R1 – Vdrop_tx * R1 / Rx, where Rx is the third resistor.

[0015] In one possible implementation, the current driving circuit includes a current source and a switching circuit; the common end of the switching circuit is coupled to the current source, and any light-emitting device is coupled to any selected end of the switching circuit; the first control signal includes: a switch control signal and a current control signal; the switching circuit is configured to: turn on the selected end coupled to the common end and the first light-emitting device according to the switch control signal to couple the current source to the first light-emitting device; the current source is configured to: provide a predetermined current to the first light-emitting device according to the current control signal.

[0016] In one possible implementation, the controller is further configured to sequentially output the first control signal corresponding to each light-emitting device to the current driving circuit based on the voltages at the output terminals of the voltage conversion circuits corresponding to the at least two light-emitting devices, in descending order or ascending order. In this way, the capacitor at the output terminal of the voltage conversion circuit is in a continuously charging or discharging state, thereby avoiding losses caused by alternating charging and discharging of the capacitor during a PRF cycle.

[0017] In a possible implementation, the voltage conversion circuit includes at least any one of the following: a boost circuit, a buck-boost circuit.

[0018] In a third aspect, a PPG sensor is provided, comprising a detector and a light-emitting device driving circuit as described in the first aspect or the second aspect; wherein the detector is used to detect a test light signal of the light-emitting device reflected and / or scattered by a detection object.

[0019] In a fourth aspect, an electronic device comprises the light-emitting device driving circuit as described in the first aspect or the second aspect, or the PPG sensor as described in the third aspect.

[0020] Among them, the technical effects brought about by any possible implementation of the third aspect and the fourth aspect can refer to the technical effects brought about by the different implementation methods of the above-mentioned first aspect or second aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the background technology, the drawings required for use in the embodiments of the present application or the background technology will be described below.

[0022] Figure 1A A top view of an electronic device provided in an embodiment of the present application;

[0023] Figure 1B A bottom view of an electronic device provided in an embodiment of the present application;

[0024] Figure 1CA schematic diagram of the internal structure of an electronic device with its back cover opened provided by an embodiment of the present application;

[0025] Figure 2 A schematic diagram of the working principle of a PPG sensor provided in an embodiment of the present application;

[0026] Figure 3 A schematic diagram of a curve showing the relationship between VF and current provided in an embodiment of the present application;

[0027] Figure 4 A schematic diagram of a power supply method for a light-emitting device provided in an embodiment of the present application;

[0028] Figure 5 A schematic structural diagram of a light emitting device driving circuit provided in an embodiment of the present application;

[0029] Figure 6 A signal timing diagram of a light emitting device driving circuit provided in an embodiment of the present application;

[0030] Figure 7 A schematic structural diagram of a light emitting device driving circuit provided in another embodiment of the present application;

[0031] Figure 8 A schematic structural diagram of a light emitting device driving circuit provided in yet another embodiment of the present application;

[0032] Figure 9 A schematic structural diagram of a light emitting device driving circuit provided in yet another embodiment of the present application;

[0033] Figure 10 A schematic structural diagram of a light emitting device driving circuit provided in another embodiment of the present application;

[0034] Figure 11 A signal timing diagram of a light emitting device driving circuit provided in another embodiment of the present application;

[0035] Figure 12 A signal timing diagram of a light emitting device driving circuit provided in yet another embodiment of the present application. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments may be part of the embodiments of the present application, but not all of the embodiments.

[0037] Unless otherwise defined, all scientific and technological terms used herein have the same meaning as those known to those of ordinary skill in the art. In this application, "at least one" refers to one or more, and "a plurality" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: the existence of A alone, the existence of A and B at the same time, and the existence of B alone, wherein A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following items" or its similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can represent: a, b, c, a and b, a and c, b and c or a, b and c, wherein a, b and c can be single or multiple. In addition, in the embodiments of the present application, words such as "first" and "second" do not limit quantity and order.

[0038] It should be noted that, in this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described in this application as "exemplary" or "for example" should not be interpreted as being more preferred or more advantageous than other embodiments or designs. To be precise, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way. In this application, unless otherwise expressly specified and limited, the term "coupling" can be a way of achieving electrical connection for signal transmission, and "coupling" can be a direct electrical connection or an indirect electrical connection through an intermediate medium.

[0039] The light-emitting device driving circuit and PPG sensor provided in the embodiments of the present application can be applied to electronic devices, such as mobile phones, tablet computers, personal computers (PCs), personal digital assistants (PDAs), smart watches, netbooks, wearable electronic devices, augmented reality (AR) devices, virtual reality (VR) devices, vehicle-mounted devices, smart cars, smart speakers, robots, smart glasses, and other different types of terminals. The embodiments of the present application do not impose any special restrictions on the specific forms of the above-mentioned electronic devices.

[0040] Take mobile phones as an example. Figures 1A to 1C 1 shows a schematic structural diagram of an electronic device 100, wherein: Figure 1A A top view of electronic device 100 is shown in accordance with the described embodiment. Figure 1B A bottom view of electronic device 100 is shown for the described embodiment. Figure 1CFIG. 1 shows a schematic diagram of the internal structure of the electronic device 100 after the back cover is opened, which illustrates a specific configuration of various internal components according to the described embodiment. Figure 1C The dotted arrow in the figure indicates the direction in which the rear cover is opened. It is understood that the structure shown in this embodiment does not constitute a specific limitation on the electronic device 100. In other embodiments of the present application, the electronic device 100 may include more or fewer components than shown, or may combine or separate certain components, or arrange the components differently.

[0041] like Figure 1A and Figure 1B As shown, electronic device 100 may include a housing 100A, which may include a front cover 101, a back cover 103, and a bezel 102. The front cover 101 and the back cover 103 are disposed opposite each other, and the bezel 102 surrounds and connects the front and back covers 101, 103. The front cover 101 may be a glass cover, with a display 192 disposed below the front cover 101. Input / output components may be disposed around the perimeter of the housing 100A. For example, a hole 105A for a front camera and a hole 106 for a receiver may be disposed at the top of the front cover 101. A button 180 may be disposed on one edge of the bezel 102, and holes 107 for a microphone, 108 for a speaker, and 109 for a USB port may be disposed at the bottom edge of the bezel 102. A hole 105B for a rear camera and a hole 105C for a PPG sensor may be disposed at the top of the back cover 103.

[0042] The housing 100A may have a cavity 104 inside, in which the internal components are encapsulated. Figure 1CAs shown, internal components can be housed in the cavity 104, and the internal components may include a printed circuit board (PCB) 110, a speaker 170A for converting an audio electrical signal into a sound signal, a receiver 170B for converting an audio electrical signal into a sound signal, a microphone 170C for converting a sound signal into an electrical signal, a USB interface 130, a front camera 193A, a rear camera 193B, and a motor 191 for generating a vibration prompt and other components. The printed circuit board 110 may be provided with a processor 120, a power management integrated circuit (PMIC) 140, at least one power amplifier (in one embodiment, including a power amplifier (PA) 152A, a power amplifier PA 152B, a power amplifier PA 152C, and a power amplifier PA 152D, where different power amplifiers PA support different frequency bands and are used to amplify transmission signals of different frequency bands. For example, the power amplifier PA 152A and the power amplifier PA 152B can be used to amplify transmission signals in a first bandwidth range, and the power amplifier PA 152C and the power amplifier PA 152D can be used to amplify transmission signals in a second bandwidth range), and at least one envelope tracking modulator (ETM) ETM for powering the power amplifier (in one embodiment, including an ET modulator ETM 151A and an ET modulator ETM 151B, where different ET modulators ETM support different bandwidths. For example, the ET modulator ETM 151A is a power amplifier PA 152A and a power amplifier PA 152D. 152B is powered, and the envelope tracking modulator ETM151B powers the power amplifier PA 152C and the power amplifier PA 152D), the switching switch 153, the antenna circuit 154 and other components. PPG sensor 160, wherein the PPG sensor 160 includes a detector 161 and a light-emitting device driving circuit 162; wherein the detector 161 is used to detect the test light signal of the light-emitting device of the light-emitting device driving circuit 162 that is reflected and / or scattered by the detection object. In addition, the printed circuit board 110 may also include components such as filters, low-noise amplifiers, audio codecs, internal memory, sensors, inductors, capacitors, etc. In order to clearly illustrate this embodiment, the filters, low-noise amplifiers, audio codecs, internal memory, sensors, inductors, capacitors, etc. are not shown. Figure 1C. The components on the printed circuit board 110 are arranged tightly so that all the components can be placed in a limited space. The arrangement of the components on the printed circuit board 110 is not limited. In some embodiments, the components on the printed circuit board 110 can be arranged on one side of the printed circuit board 110 (for example, the side facing the back cover 102). In some embodiments, the components on the printed circuit board 110 can be arranged on both sides of the printed circuit board 110 (for example, respectively on the side facing the back cover 102 and on the side facing the front cover 101).

[0043] The processor 120 may include one or more processing units, for example, an application processor (AP), a modem processor, a graphics processing unit (GPU), an image signal processor (ISP), a neural-network processing unit (NPU), a controller, a video codec, a digital signal processor (DSP), a baseband, and / or a radio frequency circuit. The controller may generate an operation control signal based on the instruction opcode and timing signal to control instruction fetching and execution.

[0044] Processor 120 may be provided with a memory for storing instructions and data. In some embodiments, the memory in processor 120 includes a cache memory. This memory can store instructions or data that have just been used or are being recycled by processor 120. If processor 120 needs to use the same instruction or data again, it can directly retrieve it from the memory. This avoids duplicate accesses, reduces processor 120 latency, and thus improves system efficiency.

[0045] The processor 120 may frequency modulate the signal according to a mobile communication technology or a wireless communication technology. Mobile communication technologies may include global system for mobile communications (GSM), general packet radio service (GPRS), code division multiple access (CDMA), wideband code division multiple access (WCDMA), time-division code division multiple access (TD-SCDMA), long term evolution (LTE), and emerging wireless communication technologies (also known as fifth generation mobile communication technologies, English: 5th generation mobile networks or 5th generation wireless systems, 5th-Generation, 5th-Generation New Radio, referred to as 5G, 5G technology or 5GNR). Wireless communication technologies may include wireless local area networks (WLAN) (such as wireless fidelity (Wi-Fi) networks), Bluetooth (BT), global navigation satellite system (GNSS), frequency modulation (FM), near field communication (NFC), infrared technology (IR), etc.

[0046] The processor 120 may also include at least one baseband and at least one radio frequency circuit. The baseband is used to synthesize the baseband signal to be transmitted and / or to decode the received baseband signal. Specifically, during transmission, the baseband encodes the voice or other data signal into the baseband signal (baseband code) to be transmitted; during reception, it decodes the received baseband signal (baseband code) into the voice or other data signal. The baseband may include components such as an encoder, a decoder, and a baseband processor. The encoder is used to synthesize the baseband signal to be transmitted, and the decoder is used to decode the received baseband signal. The baseband processor may be a microprocessor (MCU), which can be used to control the encoder and decoder. For example, the baseband processor can be used to complete the scheduling of encoding and decoding, communication between the encoder and decoder, and peripheral driving (it can enable components outside the baseband by sending an enable signal to them), etc. The RF circuit is used to process the baseband signal to form a transmit (TX) signal and pass the transmit signal to the power amplifier PA for amplification; or / and, the RF circuit is used to process the receive (RX) signal to form a baseband signal and send the formed baseband signal to the baseband for decoding. In some embodiments, each baseband corresponds to a RF circuit to frequency modulate the signal according to one or more communication technologies. For example, the first baseband and the first RF circuit frequency modulate the signal according to 5G technology, the second baseband and the second RF circuit frequency modulate the signal according to 4G technology, the third baseband and the third RF circuit frequency modulate the signal according to Wi-Fi technology, the fourth baseband and the fourth RF circuit frequency modulate the signal according to Bluetooth technology, and so on. Alternatively, the first baseband and the first RF circuit can frequency modulate the signal according to 4G technology and 5G technology at the same time, the second baseband and the second RF circuit frequency modulate the signal according to Wi-Fi technology, and so on. In some embodiments, one baseband can also correspond to multiple RF circuits to improve integration.

[0047] In some embodiments, the baseband and RF circuits may be integrated into a single integrated circuit with other components of the processor 120. In some embodiments, the baseband and RF circuits may each be a separate device independent of the processor 120. In some embodiments, a baseband and a RF circuit may be integrated into a separate device independent of the processor 120.

[0048] In the processor 120 , different processing units may be independent devices or integrated into one or more integrated circuits.

[0049] Antenna circuit 154 is used to transmit and receive electromagnetic wave signals (radio frequency signals). Antenna circuit 154 may include multiple antennas or multiple groups of antennas (multiple groups of antennas may include two or more antennas), each of which may be used to cover a single or multiple communication frequency bands. The multiple antennas may be multi-band antennas, array antennas, or on-chip antennas.

[0050] The processor 120 is coupled to the antenna circuit 154 to implement various functions associated with transmitting and receiving radio frequency signals. For example, when the electronic device 100 transmits a signal, the baseband combines the data to be transmitted (digital signal) into a baseband signal to be transmitted. The baseband signal is converted by the radio frequency circuit into a transmit signal (radio frequency signal). The transmit signal is amplified by the power amplifier. The amplified output signal of the power amplifier is transmitted to the switch 153 and transmitted through the antenna circuit 154. The path by which the transmit signal is sent from the processor 120 to the switch 153 is the transmit link (or transmit path). When the electronic device 100 needs to receive a signal, the antenna circuit 154 sends the received signal (radio frequency signal) to the switch 153. The switch 153 sends the radio frequency signal to the radio frequency circuit. The radio frequency circuit processes the radio frequency signal into a baseband signal. The radio frequency circuit converts the processed baseband signal into data and sends it to the corresponding application processor. The path by which the radio frequency signal is sent from the switch 153 to the processor 120 is the receive link (or receive path).

[0051] The switch 153 can be configured to selectively electrically connect the antenna circuit 154 to the transmit link or the receive link. In some embodiments, the switch 153 can include multiple switches. The switch 153 can also be configured to provide additional functions, including filtering and / or duplexing signals.

[0052] The SIM card interface 194 is configured to connect a SIM card. The SIM card can be inserted into or removed from the SIM card interface 194 to achieve contact and separation with the electronic device 100. The electronic device 100 can support one or N SIM card interfaces, where N is a positive integer greater than 1. The SIM card interface 194 can support Nano SIM cards, Micro SIM cards, SIM cards, and the like. Multiple cards can be inserted into the same SIM card interface 194 at the same time. The types of the multiple cards can be the same or different. Each SIM card can support one or more communication standards, each of which has a specified frequency band and a different maximum bandwidth. The SIM card interface 194 can also be compatible with different types of SIM cards. The SIM card interface 194 can also be compatible with external storage cards. The electronic device 100 interacts with a network through the SIM card to achieve functions such as calling and data communication. In some embodiments, the electronic device 100 uses an eSIM, i.e., an embedded SIM card. The eSIM card can be embedded in the electronic device 100 and cannot be separated from the electronic device 100.

[0053] The PMIC 140 is configured to manage power in the electronic device 100. For example, the PMIC 140 can include a charging management circuit and a power supply management circuit. The charging management circuit is configured to receive a charging input from a charger, for example, in some wired charging embodiments, the charging management circuit can receive a charging input from a wired charger through the USB interface 130. The power supply management circuit is configured to receive an input of the battery 141 and / or the charging management circuit, and supply power to components such as the processor 120, the display 192, the front camera 193A, the rear camera 193B, and the motor 191. In other embodiments, the charging management circuit and the power supply management circuit can also be disposed in the processor 120. In other embodiments, the charging management circuit and the power supply management circuit can also be disposed in different devices.

[0054] Specific embodiments of the present application provide a light emitting device driving circuit including at least one light emitting device, which can be used in the backlight module of the display 192 described above, or which can also be used in the PPG sensor described above. Wherein, the backlight module is mainly used to provide backlight for the display 192 to display. In combination with the above description of the PPG sensor, the light emitting device driving circuit can be used in the PPG sensor. Figure 2 As shown, the basic principle of the PPG sensor is that a test light signal is emitted by the light emitting device, a part of the test light signal is emitted at the detection object (for example, inside the skin or the skin interface); a part of the test light signal is scattered at the detection object (for example, inside the skin), and a part of the scattered signal will return to the PPG sensor and be received by the detector of the PPG sensor, which is called the backscattering signal. In addition to being able to receive a part of the scattered signal, the detector will also receive a part of the reflected signal.

[0055] Generally, the light emitted by the backlight module or the PPG sensor is usually implemented by multiple wavelengths, and each wavelength corresponds to a light emitting device (for example: laser diode (LD), light-emitting diode (LED), organic light-emitting diode (OLED), vertical-cavity surface-emitting laser (VCSEL), etc.); of course, one light emitting device can also emit light of different wavelengths under different currents. Taking the PPG sensor as an example, the PPG sensor on the wearable product generally adopts three wavelengths, namely green light, red light and infrared (IR) light. The center wavelength of the green light emitting device is generally 530 nm, the center wavelength of the red light emitting device is generally 670 nm, and the center wavelength of the infrared light emitting device is generally 850 nm or 900 nm or 940 nm. Different center wavelengths of light emitting devices are processed by different materials, and the process also has certain differences, so when a certain current flows through the light emitting device with different center wavelengths, the voltage drop generated on the light emitting device is different. This voltage drop is the forward voltage drop (Forward Voltage, abbreviated as VF) of the light emitting device. As shown in Figure 3 , it is a VF (V) vs. current (mA) relationship diagram of the light emitting devices (taking LED as an example) of three colors (G, R, IR). As shown in Figure 4 , in the electronic device, the power supply generally provides a fixed voltage to the light emitting device, and the current source controls the current I flowing through the light emitting device to control the light emitting intensity of the light emitting device. Generally, increasing the current I flowing through the light emitting device increases the light emitting intensity of the light emitting device; reducing the current I flowing through the light emitting device reduces the light emitting intensity of the light emitting device. Since there is internal resistance in the light emitting device, when the current flowing through the light emitting device changes, the VF on the light emitting device also changes. For example: assuming that the internal resistance of the light emitting device is 10 ohm, when 10 mA current flows through the light emitting device, a 0.1 V voltage drop will be formed between the anode and the cathode of the light emitting device; when 100 mA flows through the light emitting device, a 1 V voltage drop will be formed between the anode and the cathode of the light emitting device. Therefore, not only are there differences in VF of light emitting devices of different colors (different wavelengths), but also there are differences in VF of light emitting devices of the same color (wavelength) under different currents, and generally VF increases with the increase of the current flowing through.

[0056] Taking LED (Dg, Dr, Dir; wherein Dg is a green LED, Dr is a red LED, and Dir is an infrared LED) as an example, generally, in the PPG sensor or the backlight module, the LED is Figure 5 The power supply and drive method shown in the figure. The input terminal of the voltage conversion circuit 51 (for example, the voltage conversion circuit 51 can use a boost circuit or a buck-boost circuit) inputs the system voltage (Vsys), and the output terminal Vout powers one or more LEDs (Dg, Dr, Dir) of different wavelengths (for example, connected to the anode (Anode) of the LED). The cathode of the LED (Dg, Dr, Dir) is connected to the current drive circuit 52 (TxDriver). The current drive circuit 52 generally includes a current source 522 and a switching circuit 521. When the current source 522 is connected to the cathode (cathode) of a certain LED (for example, it can be one of Dg, Dr, and Dir) through the switching circuit 521, current will flow through the connected LED, causing it to emit light. The current provided by the current source 522 and the opening or closing of the switching circuit 521 are controlled by their respective control signals. In order to ensure that all LEDs (Dg, Dr, Dir) can work normally at the maximum current, the voltage output by the voltage conversion circuit 51 needs to be set to a voltage that can allow the LED with the largest VF to operate at the maximum current. For example: the voltage drop of the current source 522 at the maximum current is Vhr_max = 0.6V, the maximum current is: Imax = 200mA, and the maximum voltage drops of the three LEDs Dg, Dr, and Dir at Imax are VF_Gmax = 4.3V, VF_Rmax = 3.9V, and VF_IRmax = 2.0V respectively. Therefore, the output voltage of the voltage conversion circuit 51 needs to be fixed at Vout = Vhr_max + maxim{VF_Gmax, VF_Rmax, VF_Irmax} + Vmargin = 5.0V (Vmargin is the engineering margin, which can be 0, and is set to 0.1V here). When the LED is working, the voltage drop on the current source 522 (the voltage drop of the current driving circuit 52, or the voltage from the cathode of the LED to the negative terminal of the current source 522, Figure 5 The negative terminal of the current source 521 is connected to the ground terminal GND, and the voltage is 0V). Vdrop_tx = Vout – {VF_G, VF_R, VF_Ir}. When the output terminal Vout of the voltage conversion circuit 51 is powered by 5V, when Dg is operating at 200mA, the voltage drop Vdrop_tx on the current source 522 is 0.6V (not considering the engineering margin), which just meets the voltage requirement for normal operation of the current source 522 (i.e., the voltage margin, headroom voltage). However, when Dr or Dir is operating, since the VF of Dr and Dir is lower than that of Dg, the voltage drop Vdrop_tx on the current source 522 is 1V and 2.9V respectively. Figure 6As shown in the figure. During one pulse repetition frequency (PRF, such as PRF#1 or PRF#2 in the figure) of the lighting timing of each LED, Dr and Dir are working, Vdrop_tx of current source 522 is much larger than the required Headroom voltage of 0.6V, and the increase of Vdrop_tx during the lighting of Dr and Dir is the power consumption waste relative to Dg. When Dr and Dir work at 200mA, the additional waste voltage drop is 0.4V and 2.3V respectively, accounting for 8% and 46% of the 5V output voltage of voltage conversion circuit 51. Generally, the working current of LEDs of G, R, IR three wavelengths is much smaller than 200mA. Then, when Dg works, it will also cause additional voltage drop on current driving circuit 52, for example, the smaller the working current, the higher the proportion of additional waste voltage drop. In summary, in order to be compatible with the maximum current working scene of LEDs of multiple wavelengths or compatible with the working scene of LEDs of single wavelength under different currents, the LED of PPG sensor is powered by voltage conversion circuit 51, and the voltage conversion circuit 51 outputs a fixed maximum voltage to meet the normal working needs of the limit (maximum current) scene. For LEDs with relatively low VF, or when LEDs work in a non-maximum current working scene, the fixed maximum voltage output by voltage conversion circuit 51 will cause great waste and reduce the endurance of the electronic device.

[0057] To solve the above problems, an embodiment of the present application provides a light emitting device driving circuit. Referring to Figure 7 、 Figure 8 As shown in the figure, it comprises: a voltage conversion circuit 71, at least one light emitting device (Dg, Dr and Dir), a current driving circuit 72 and a controller 73; any light emitting device (Dg, Dr and Dir) and the current driving circuit 72 are connected in series between the output end Vout of the voltage conversion circuit 71 and the ground end GND. It should be noted that in the embodiments of the present application, the series relationship of the light emitting device and the current driving circuit 72 is not limited, for example, referring to Figure 7 As shown in the figure, one end of any light emitting device (Dg, Dr and Dir) is connected to the output end of the voltage conversion circuit 71, the other end of the light emitting device is connected to one end of the current driving circuit 72, and the other end of the current driving circuit 72 is connected to the ground end GND. In Figure 8 , one end of the current driving circuit 72 is connected to the output end of the voltage conversion circuit 71, and the other end of the one end of the current driving circuit 72 is connected to one end of any light emitting device (Dg, Dr and Dir). The other end of the light emitting device (Dg, Dr and Dir) is connected to the ground end GND. Taking the LED as an example, in the example of Figure 7 , the anode of the LED is connected to the output end of the voltage conversion circuit 71, and the cathode of the LED is connected to the current driving circuit 72; in Figure 8 In the example, the anode of the LED is connected to the current driving circuit 72, and the cathode of the LED is connected to the ground terminal GND.

[0058] Among them, the controller 73 is configured to: output a first control signal to the current driving circuit 72; the current driving circuit 72 is configured to: provide a predetermined current to the first light-emitting device (one of Dg, Dr and Dir) according to the first control signal; the controller 73 is configured to: output a second control signal to the voltage conversion circuit 71 according to the electrical parameters on the path where the first light-emitting device and the current driving circuit 72 are located; the voltage conversion circuit 71 is configured to: adjust the voltage at the output end of the voltage conversion circuit 71 according to the second control signal.

[0059] In this way, when the controller controls the current driving circuit to output a predetermined current to the first light-emitting device in at least one light-emitting device through a first control signal, the controller can output a second control signal to the voltage conversion circuit according to the electrical parameters on the path between the first light-emitting device and the current driving circuit; then, the voltage conversion circuit can adjust the voltage at the output end in real time according to the second control signal, and no longer work according to the limit (maximum current) scenario that meets the light-emitting device to supply power to all light-emitting devices with the maximum fixed voltage, thereby improving the power supply efficiency of the light-emitting device to reduce the power consumption of the entire machine.

[0060] For example, refer to Figure 7 or Figure 8 As shown, the current driving circuit 72 includes a current source 722 and a switching circuit 721; the common terminal ct of the switching circuit 721 is coupled to the current source 722, and any light emitting device (Dg, Dr and Dir) is coupled to any selected terminal of the switching circuit 721 (such as Figure 7 or Figure 8As shown, the switching circuit 721 includes three selection terminals c1, c2, and c3, wherein the light-emitting device Dg is coupled to the selection terminal c1, the light-emitting device Dr is coupled to the selection terminal c2, and the light-emitting device Dir is coupled to the selection terminal c3. The first control signal includes a switch control signal and a current control signal. The switching circuit 721 is configured to, in accordance with the switch control signal, conduct the common terminal ct to the selection terminal coupled to the first light-emitting device, thereby coupling the current source 722 to the first light-emitting device. For example, when the common terminal ct is conducted to the selection terminal c1, the current source 722 is coupled to the light-emitting device Dg. The switch control signal is synchronized with the lighting timing of the first light-emitting device, i.e., when the switch control signal controls the current source 722 to be coupled to the first light-emitting device, the first light-emitting device is illuminated. The current source 722 is configured to provide a predetermined current to the first light-emitting device in accordance with the current control signal. In addition, the first control signal and the second control signal corresponding to the same first light-emitting device need to be processed synchronously. For example, the second control signal controls the voltage conversion circuit 71 only when the first control signal controls the current driving circuit 72 to drive the first light-emitting device to light up, or before the first control signal controls the current driving circuit 72 to drive the first light-emitting device to light up, or after the first control signal controls the current driving circuit 72 to drive the first light-emitting device to light up. The advance or lag (delay) time can be configured arbitrarily.

[0061] In a specific implementation, referring to Figure 9As shown, the voltage drop of current source 722 (TxDriver voltage drop) or headroom voltage can be used to achieve automatic voltage regulation of voltage conversion circuit 71. In this way, the electrical parameter includes the voltage drop of current source 722. Controller 73 is configured to detect the voltage drop of current source 722 and output a second control signal to voltage conversion circuit 71 based on the voltage drop of current source 722. When the voltage drop of current source 722 is greater than a set threshold, the second control signal is used to control voltage conversion circuit 71 to reduce the voltage at the output terminal. When the voltage drop of current source 722 is less than the set threshold, the second control signal is used to control voltage conversion circuit 71 to increase the voltage at the output terminal. For example, if the voltage drop of TxDriver or headroom voltage is greater than a set threshold (e.g., 0.7V), the output voltage of voltage conversion circuit 71 is reduced; if the voltage drop of Tx Driver or headroom voltage is less than the set threshold (e.g., 0.7V), the output voltage of voltage conversion circuit 71 is increased. In this way, the additional voltage drop of Tx Driver or headroom voltage is reduced, reducing system power consumption. However, in this example, since it is necessary to first obtain the voltage drop of the current source 722 before outputting the second control signal to the voltage conversion circuit 71 based on the voltage drop of the current source 722, the timing of the first control signal should be earlier than the second control signal. After the first control signal controls the current drive circuit 72 to drive the LED to light up, the second control signal performs voltage regulation control on the voltage conversion circuit 71.

[0062] Optionally, the second control signal can directly include the voltage drop of current source 722 (the voltage drop of the Tx Driver, Vdrop_tx) or the headroom voltage. Specifically, the controller 73 can directly output the voltage drop, Vdrop_tx, or headroom voltage of current source 722 to the voltage conversion circuit 71. This voltage drop of current source 722 controls the output voltage of the voltage conversion circuit 71. In this case, the voltage conversion circuit 71 is capable of receiving a voltage control signal (i.e., the aforementioned second control signal) and further has the function of adjusting a set threshold. When the voltage drop of the input current source 722 falls below the set threshold, the output voltage of the voltage conversion circuit 71 is increased; when the voltage drop of the input current source 722 exceeds the set threshold, the output voltage of the voltage conversion circuit 71 is decreased. This negative feedback mechanism allows the output voltage of the voltage conversion circuit 71 to be adjusted and stabilized. Furthermore, the voltage conversion circuit 71 can adjust the set threshold through hardware (e.g., resistor divider) or software (e.g., configuring registers via an I2C (inter-integrated circuit) interface).

[0063] In another specific implementation, combined with Figure 7 or Figure 8 As shown, the electrical parameters include the driving current of the first light-emitting device; the controller 73 is configured to output a second control signal to the voltage conversion circuit 71 according to the driving current of the first light-emitting device. The driving current of the first light-emitting device can be used to achieve automatic voltage regulation of the voltage conversion circuit 71. In this way, the electrical parameters include the driving current of the first light-emitting device. For example, if the current of the current source 722 increases or the driving current of the first light-emitting device (of course, in a series circuit, the current of the current source 722 is equal to the driving current of the first light-emitting device) increases, the output voltage of the voltage conversion circuit 71 is increased; if the current of the current source 722 increases or the driving current of the first light-emitting device decreases, the output voltage of the voltage conversion circuit 71 is decreased. In this way, the voltage drop or headroom voltage of the additional current source 722 is reduced, thereby reducing the power consumption of the system.

[0064] Specifically, the controller 73 is specifically configured to query the expected voltage value corresponding to the driving current of the first light-emitting device according to the lookup table, and output a second control signal to the voltage conversion circuit 71 according to the expected voltage value. The second control signal is used to control the voltage conversion circuit to output the expected voltage value at the output end.

[0065] Referring to the lookup table shown in Table 1, assuming that Dg, Dr, and Dir are sequentially turned on, with the drive currents of Dg, Dr, and Dir being 100mA, 50mA, and 200mA, respectively, the first control signals corresponding to Dg, Dr, and Dir are used to obtain the expected voltage values ​​to be output by voltage conversion circuit 71 by looking up the first, second, and third rows of Table 1, respectively, before or after controlling Dg, Dr, and Dir to turn on. These values ​​are then used to control voltage conversion circuit 71 to output 4.6V, 3.4V, and 2.8V. The lookup table can be stored in voltage conversion circuit 71, in controller 73, or in a dedicated storage space independent of controller 73 (e.g., a memory in an electronic device) and operated by controller 73 (e.g., by querying the lookup table stored in the storage space based on the drive current of the first light-emitting device and the type of the light-emitting device to obtain the expected voltage value). If the lookup table is stored in the voltage conversion circuit 71, the controller 73 can first obtain the desired voltage value by querying the lookup table, and then output a second control signal to the voltage conversion circuit 71 to control the voltage conversion circuit 71 to output the desired voltage value. Alternatively, the controller 73 outputs the driving current of the first light-emitting device and the type of the light-emitting device (which may be included in the second control signal) to the voltage conversion circuit 71. The voltage conversion circuit 71 then queries the lookup table based on the driving current and type of the first light-emitting device to obtain the desired voltage value and adjusts the output voltage to the desired voltage value. The controller 73 can directly control the voltage conversion circuit 71 to output the desired voltage value through a control interface, or can control the voltage conversion circuit 71 to output the desired voltage value through software (e.g., configuring registers via an I2C interface).

[0066]

[0067] Table 1

[0068] In another embodiment, the controller 73 is specifically configured to calculate the expected voltage value corresponding to the driving current of the first light-emitting device according to a set formula, and output a second control signal to the voltage conversion circuit according to the expected voltage value. The second control signal is used to control the voltage conversion circuit to output the expected voltage value at the output end.

[0069] Specifically, the expected voltage value output by the voltage conversion circuit 71 can be obtained by setting a formula. For example, the relationship between the expected voltage value and the driving current of the first light emitting device can be described by a linear polynomial or a quadratic polynomial.

[0070] For example, Vout(i)=b(i)*I led (i)+c(i), i is used to represent light-emitting devices of different colors (such as G, R, IR), b(i), c(i) are the coefficients of a linear polynomial, I led(i) represents the driving current of the light emitting device.

[0071] Or, Vout(i)=a(i)*I led (i)*I led (i)+b(i)*I led (i)+c(i),a(i),b(i),c(i) are the coefficients of a quadratic polynomial.

[0072] Taking a first-order polynomial as an example, Vout_green=0.00444*I led_Green +3.41;

[0073] Vout_red=0.005*I led_Red +2.5;

[0074] Vout_ir=0.00333*I led_IR +1.43.

[0075] It should be noted that if the calculated Vout(i) is only the VF of the LED, then the expected voltage value output by the voltage conversion circuit 71 must be equal to Vout(i) plus the voltage drop of the current source 722. If the voltage drop of the current source 722 is taken into account in the setting formula, that is, c(i) already includes the voltage drop of the current source 722, then Vout(i) is directly used as the expected voltage value output by the voltage conversion circuit 71.

[0076] A set formula representing the relationship between each light-emitting device or the driving current and the desired voltage value for each light-emitting device can be pre-stored in the voltage conversion circuit 71, the controller 73, or a dedicated storage space (e.g., a memory in an electronic device). When a light-emitting device needs to be illuminated, the set formula for the corresponding light-emitting device is obtained based on the driving current and type of the light-emitting device. The desired output voltage value Vout(i) of the voltage conversion circuit 71 is then calculated based on the driving current of the light-emitting device and the set formula. The controller 73 can calculate Vout(i) and then output a corresponding second control signal to the voltage conversion circuit 71 to control the voltage conversion circuit 71 to adjust the output voltage according to Vout(i). The calculation of Vout(i) can also be implemented in the voltage conversion circuit 71. The controller 73 provides the driving current and type of the light-emitting device to the voltage conversion circuit 71 via a second control signal. The voltage conversion circuit 71 calculates Vout(i) according to the set formula and then adjusts the output voltage based on Vout(i).

[0077] In another example, referring to Figure 10As shown, an embodiment of the present application provides a light-emitting device driving circuit, including: a voltage conversion circuit 71, at least one light-emitting device (Dg, Dr, and Dir), a current driving circuit 72, and a controller 73; the voltage conversion circuit 71 includes a feedback terminal FB and an output terminal Vout, wherein a first resistor R1 and a second resistor R2 are connected in series between the output terminal Vout and the ground terminal GND; the connection point of the first resistor R1 and the second resistor R2 is coupled to the feedback terminal FB; the first light-emitting device (one of Dg, Dr, and Dir) is connected in series between the output terminal Vout and the current driving circuit 72, and a third resistor is coupled between the connection point between the first light-emitting device (one of Dg, Dr, and Dir) and the current driving circuit 72 and the feedback terminal FB. Exemplarily, Figure 10 Three light-emitting devices Dg, Dr and Dir are shown in the figure, wherein a resistor R5 is coupled between the connection point of Dg and the current driving circuit 72 and the feedback terminal FB; a resistor R4 is coupled between the connection point of Dr and the current driving circuit 72 and the feedback terminal FB, and a resistor R3 is coupled between the connection point of Dir and the current driving circuit 72 and the feedback terminal FB.

[0078] The controller 73 is configured to output a first control signal to the current driving circuit 72; the current driving circuit 72 is configured to provide a predetermined current to the first light-emitting device according to the first control signal; the voltage conversion circuit 71 is configured to control the voltage of the output terminal Vout to be reduced when it is determined that the first voltage of the feedback terminal FB is higher than the predetermined voltage value; or to control the voltage of the output terminal Vout to be increased when it is determined that the second voltage of the feedback terminal FB is lower than the predetermined voltage value.

[0079] Specific, combined Figure 10As shown, when R3, R4, R5 are not set, the output voltage Vout of the voltage conversion circuit 71 is determined by R1 and R2, i.e. Vout = Vref*(R1+R2) / R2, Vref being the reference comparison voltage inside the feedback end (FB). The working principle of the voltage conversion circuit 71 is that when the voltage of the feedback end FB is greater than Vref, the voltage conversion circuit 71 lowers the output voltage of Vout; when the voltage of the feedback end FB is less than Vref, the voltage conversion circuit 71 increases the output voltage of Vout. Through such feedback control, the voltage of the feedback end FB is finally stabilized at Vref, i.e. the voltage of the output end Vout of the voltage conversion circuit 71 is stabilized at Vref*(R1+R2) / R2. In this way, it is possible to connect a resistance from one end of each light emitting device (the cathode of the LED) to the feedback end FB of the voltage conversion circuit 71 to realize automatic regulation of the voltage of the output end Vout of the voltage conversion circuit 71. The specific process is as follows (assuming that the driving current of each light emitting device is fixed), after the voltage conversion circuit 71 is started, no current flows through the light emitting device, and the output voltage Vout is Vref*(R1+R2) / R2 (the actual LED will have a weak current flowing through, resulting in a change in the output voltage, but this does not affect the process analysis); the predetermined current output by the current driving circuit 72 flows through the voltage of the selected first light emitting device, and a voltage drop is formed in the current driving circuit 72. The voltage drop of the current driving circuit 72 increases, and the voltage of the feedback end FB is raised, and when the first voltage of the feedback end FB is higher than the predetermined voltage value, the voltage conversion circuit 71 lowers the output voltage of Vout. After the output voltage Vout of the voltage conversion circuit 71 is lowered, since the voltage drop of the first light emitting device is unchanged, the voltage drop of the current driving circuit 72 is lowered, causing the voltage of the feedback end FB to be lowered. Finally, the voltage of the feedback end FB is maintained at the critical state of Vref. Finally, the voltage Vout of the output end Vout of the voltage conversion circuit 71 is Vout = Vref*[1 / Rx+1 / R2+1 / R1]*R1– Vdrop_tx*R1 / Rx; where Rx is the resistance connected to the cathodes of Dg, Dr and Dir of the feedback end FB, i.e. Figure 10 R3, R4, R5 in FIG. 1.

[0080] Assuming R1 = 3Mohm, R2 = 800Kohm, and R5 = 3Mohm, when Dg is on, if the voltage drop Vdrop_tx of the current driving circuit 72 is 0.6V, the voltage Vout at the output terminal Vout of the voltage conversion circuit 71 can be controlled to be 5.15V; if the voltage drop Vdrop_tx of the current driving circuit 72 is 0.7V, the voltage Vout at the output terminal Vout of the voltage conversion circuit 71 can be controlled to be 5.05V; if the voltage drop Vdrop_tx of the current driving circuit 72 is 1V, the voltage Vout at the output terminal Vout of the voltage conversion circuit 71 is adjusted to be 4.75V. This is shown in Table 2:

[0081] Vdrop_tx Vout VF_G Maximum current Dg can support (mA) 0.6 5.15 4.55 >200 0.7 5.05 4.35 200 0.8 4.95 4.15 160 0.9 4.85 3.95 100 1 4.75 3.75 80 1.2 4.55 3.35 40

[0082] Table 2

[0083] As can be seen from Table 2, if Dg operates at 40mA and the voltage conversion circuit 71 is configured to output a fixed 5.15V, an additional 0.6V (5.15-4.55) voltage drop is wasted on the current drive circuit 72. The automatic voltage regulation control of this solution can reduce the additional voltage waste on the current drive circuit 72, thereby improving the power supply efficiency of the light-emitting device and reducing the overall power consumption.

[0084] Optional, see Figure 10 As shown, the current driving circuit 72 includes a current source 722 and a switching switch circuit 721; the common end of the switching switch circuit 721 is coupled to the current source 722, and any light-emitting device is coupled to any selected end of the switching switch circuit 721; the first control signal includes: a switch control signal and a current control signal; the switching switch circuit 721 is configured to: turn on the selected end coupled to the common end and the first light-emitting device according to the switch control signal to couple the current source 722 to the first light-emitting device; the current source 722 is configured to: provide a predetermined current to the first light-emitting device according to the current control signal.

[0085] It should be noted that the controllers provided in the above embodiments can directly reuse the above Figure 1C The processor 120 shown, or the controller in the embodiment of the present application can be Figure 1C The chip or processor 120 with control function in the electronic device is configured and managed.

[0086] In addition, in an example, when the voltage of the output terminal Vout of the voltage conversion circuit 71 is dynamically adjusted in the above manner, the waveforms of the corresponding signal timings are as follows: Figure 11 As shown, the switch control signal is output by the controller 73 to the current driving circuit 72, which controls the switching circuit 721 to turn on each light emitting device and the current source one by one (as shown in FIG. Figure 11As shown, when Dg is controlled to be turned on with the current source, Dg is turned on, and current at the output end of the voltage conversion circuit 71 will flow from the anode of Dg to the cathode, and then flow through the current source to the ground through the switching circuit 721. The current size is determined by the current size set by the current source, which is specifically controlled by the current control signal. The driving current is the current size of the current source set according to the lighting sequence of each light-emitting device. Among them, after the voltage at the output end Vout of the voltage conversion circuit 71 is dynamically adjusted in the above manner (as shown in FIG. Figure 11 As shown, during the Dg-on period, the driving current is 100mA, and the output end Vout of the voltage conversion circuit 71 is 4.6V; during the Dr-on period, the driving current is 50mA, and the output end Vout of the voltage conversion circuit 71 is 3.4V; during the Dir-on period, the driving current is 200mA, and the output end Vout of the voltage conversion circuit 71 is 2.8V). The voltage drop Vdrop_tx of the current driving circuit 72 is stabilized at the same voltage value of 0.6V, reducing the extra voltage waste on the current driving circuit 72, thereby improving the power supply efficiency of the light-emitting device and reducing the power consumption of the entire device.

[0087] In actual operation, the voltage conversion circuit 71 adopts a boost circuit. Figure 12 The figure shows the timing relationship between the output voltage of a boost circuit and the lighting of a light-emitting device. In actual circuits, the output of a boost circuit is typically grounded via a capacitor. This capacitor is primarily used to remove high-frequency noise coupled to the boost circuit and store energy, maintaining a relatively constant voltage at the output terminal Vout of the boost circuit and reducing noise on the voltage at the output terminal Vout. Between the lighting of two light-emitting devices, there is a period of inactivity, which allows the system to perform other processing. In the figure, toff>0. To ensure the measurement performance of the PPG sensor, the supply voltage to the light-emitting device must remain constant (considering the headroom voltage of the current drive circuit 72) or remain above the voltage required to maintain the device operating at the set current during or for most of the lighting process (when the switch control signal turns the light-emitting device on, such as during the Dg, Dr, or Dir on-state). Assuming the lighting time is ton (not shown in the figure), the time during which the supply voltage remains stable or remains above the voltage required to maintain the device operating at the set current (considering the headroom voltage of the current drive circuit 72) is tvs (not shown in the figure). When tvs>ton, the boost circuit's supply voltage can cover the entire lighting time ton, allowing the light-emitting device to operate normally during the entire lighting time ton. Of course, it is also possible for tvs<=ton. In this case, the boost circuit's supply voltage can cover a portion of the lighting time ton, allowing the light-emitting device to operate normally. Figure 12tr (tr1, tr2) represents the output voltage rise time (rise time) when the boost circuit adjusts from a low voltage (or 0V output) to a high voltage, tr1 represents the start time of Dg lighting or before or after the start time in each PRF ( Figure 12 (before), the rise time of the boost circuit output from 0V to the expected voltage of 4.6V. td (td1, td2 and td3) represents the time it takes for the output voltage of the boost circuit to drop from a high level to a low level. Figure 12 Here, td1 represents the time it takes for the boost circuit's output voltage to drop from the desired 4.6V voltage for Dg lighting to 3.4V for Dr lighting. Because the boost circuit's output is typically grounded via a relatively large capacitor, the capacitor must discharge to drop the boost circuit's output voltage from a high level to a low level. Therefore, td is typically quite long. For the same voltage difference, td is generally greater than (much greater than) tr. That is, when the capacitor changes the same voltage difference during charging and discharging, the discharge time is much greater than the charging time. Of course, if power consumption is not a concern, the output of the adjustable boost circuit can also be grounded during toff, quickly releasing the voltage stored in the capacitor connected to the boost circuit's output. In this case, td and tr can be made equal for the same voltage difference during charging and discharging.

[0088] In practice, to further conserve power, the boost circuit can be disabled during the toff phase to reduce the power consumed by the boost circuit itself. Furthermore, leakage losses in the boost circuit and capacitors when they are off can be reduced through design. For example, the boost circuit's resistance to ground can be increased through design or process, or capacitors with low leakage can be used.

[0089] In actual use, the lighting order of the light-emitting devices can be configured according to the high and low sorting of the expected voltage output by the boost circuit. Therefore, the controller is also configured to output the first control signal corresponding to each light-emitting device to the current driving circuit in sequence according to the voltage of the output end of the voltage conversion circuit corresponding to at least two light-emitting devices from large to small or from small to large. Figure 12 The lighting sequence of at least one light-emitting device can be controlled in descending order of the desired voltage output by the boost circuit. Alternatively, the lighting sequence of at least one light-emitting device can be controlled in descending order of the desired voltage output by the boost circuit. In this way, the voltage at the output end of the boost circuit can change in a certain order during the lighting process of each light-emitting device. Thus, during a PRF cycle, the boost capacitor is in a continuous charging or discharging state, avoiding losses caused by alternating charging and discharging of the capacitor during a PRF cycle.

[0090] In the above embodiments, the boost circuit may have one or more of a bypass function and a down mode function. If the boost circuit does not have a bypass function, when the desired voltage value output by the boost circuit is lower than the minimum output voltage of the boost circuit, the boost circuit outputs at the minimum output voltage. If the boost circuit has a bypass function but does not have a down mode function, when the desired voltage value output by the boost circuit is lower than or equal to the input voltage (Vin) of the boost circuit, the boost circuit outputs at the input voltage Vin. In the above two boost circuits, when the desired voltage value output by the boost circuit is lower than the input voltage (Vin) of the boost circuit, the output voltage of the adjustable boost circuit is still Vin, then the voltage difference between Vin and the desired voltage value output by the boost circuit will be superimposed on the headroom voltage of the current driving circuit 72, increasing the voltage drop on the current driving circuit 72, resulting in additional power consumption waste. If the boost circuit has both a bypass function and a down mode function, then when the desired voltage value output by the boost circuit is lower than or equal to the input voltage (Vin) of the boost circuit, the boost circuit outputs the desired voltage value. The voltage difference between Vin and the desired voltage value will fall on the boost circuit and be consumed by the boost circuit. At this time, the head room voltage on the current drive circuit 72 does not increase, and the extra power consumption is wasted on the boost circuit. To solve this problem, the above-mentioned boost circuit can be replaced with a buck-boost circuit to further reduce the extra power consumption. When the desired voltage value is lower than the buck-boost input voltage, the buck-boost circuit operates in buck mode, and the buck-boost circuit pumps the higher input voltage to a lower output voltage. When the desired voltage value is higher than the buck-boost input voltage, the buck-boost circuit operates in boost mode, and the buck-boost circuit pumps the lower input voltage to a higher output voltage. When the desired voltage value is approximately equal to the input voltage of the buck-boost circuit, the buck-boost circuit can operate in bypass mode (i.e., pass-through mode), and the buck-boost circuit directly outputs the input voltage to the output terminal as the output voltage.

[0091] The above-mentioned voltage conversion circuit, controller, current driving circuit, memory, etc. can be integrated into the same chip in any combination, or separated into different chips on the PCB. For example, they can all be integrated into the analog front end (AFE) chip.

[0092] In the above embodiments, the description of each embodiment has different emphases. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0093] Although the present application has been described with reference to specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present application. Accordingly, this specification and the drawings are merely illustrative of the present application as defined by the appended claims and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present application. Obviously, those skilled in the art may make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, the present application is intended to include such modifications and variations as fall within the scope of the claims of the present application and their equivalents.

Claims

1. A light emitting device driving circuit, characterized in that: include: A voltage conversion circuit, at least two light-emitting devices, a current driving circuit, and a controller; any of the light-emitting devices and the current driving circuit are connected in series between the output terminal of the voltage conversion circuit and the ground terminal; The controller is configured to: output a first control signal to the current driving circuit; The current driving circuit is configured to: provide a predetermined current to the first light emitting device according to the first control signal; The controller is configured to: output a second control signal to the voltage conversion circuit according to electrical parameters on a path between the first light emitting device and the current driving circuit; The voltage conversion circuit is configured to: adjust the voltage of the output terminal of the voltage conversion circuit according to the second control signal; The controller is further configured to output the first control signal corresponding to each light-emitting device to the current driving circuit in sequence according to the voltage of the output end of the voltage conversion circuit corresponding to the at least two light-emitting devices from large to small or from small to large.

2. The light emitting device driving circuit according to claim 1, wherein: The current driving circuit includes a current source and a switching circuit; a common terminal of the switching circuit is coupled to the current source, and any of the light-emitting devices is coupled to any selected terminal of the switching circuit; The first control signal includes: a switch control signal and a current control signal; The switching circuit is configured to: turn on the selection terminal coupled between the common terminal and the first light-emitting device according to the switch control signal, so as to couple the current source to the first light-emitting device; The current source is configured to provide a predetermined current to the first light emitting device according to the current control signal.

3. The light emitting device driving circuit according to claim 1 or 2, characterized in that: The electrical parameters include a voltage drop of the current driving circuit; The controller is configured to detect the voltage drop of the current driving circuit and output the second control signal to the voltage conversion circuit according to the voltage drop; wherein, when the voltage drop is greater than a set threshold, the second control signal is used to control the voltage conversion circuit to lower the voltage of the output end; when the voltage drop is less than the set threshold, the second control signal is used to control the voltage conversion circuit to increase the voltage of the output end.

4. The light emitting device driving circuit according to claim 1 or 2, characterized in that: The electrical parameters include a driving current of the first light emitting device; The controller is configured to output the second control signal to the voltage conversion circuit according to the driving current of the first light emitting device.

5. The light emitting device driving circuit according to claim 4, characterized in that: The controller is specifically configured to query the expected voltage value corresponding to the driving current of the first light-emitting device according to a lookup table, and output the second control signal to the voltage conversion circuit according to the expected voltage value, and the second control signal is used to control the voltage conversion circuit to output the expected voltage value at the output end.

6. The light emitting device driving circuit according to claim 4, characterized in that: The controller is specifically configured to calculate the expected voltage value corresponding to the driving current of the first light-emitting device according to a set formula, and output the second control signal to the voltage conversion circuit according to the expected voltage value, and the second control signal is used to control the voltage conversion circuit to output the expected voltage value at the output end.

7. The light emitting device driving circuit according to claim 1, characterized in that: The voltage conversion circuit includes at least any one of the following: a boost circuit and a buck-boost circuit.

8. A light emitting device driving circuit, characterized in that: include: A voltage conversion circuit, at least one light-emitting device, a current driving circuit and a controller; The voltage conversion circuit includes a feedback terminal and an output terminal, wherein a first resistor and a second resistor are connected in series between the output terminal and a ground terminal; a connection point between the first resistor and the second resistor is coupled to the feedback terminal; a first light-emitting device is connected in series between the output terminal and the current driving circuit, and a third resistor is coupled between a connection point between the first light-emitting device and the current driving circuit and the feedback terminal; The controller is configured to: output a first control signal to the current driving circuit; The current driving circuit is configured to: provide a predetermined current to the first light emitting device according to the first control signal; The voltage conversion circuit is configured to control the voltage of the output terminal to decrease when it is determined that the first voltage of the feedback terminal is higher than a predetermined voltage value; or to control the voltage of the output terminal to increase when it is determined that the second voltage of the feedback terminal is lower than a predetermined voltage value.

9. The light emitting device driving circuit according to claim 8, characterized in that: The current driving circuit includes a current source and a switching circuit; a common terminal of the switching circuit is coupled to the current source, and any of the light-emitting devices is coupled to any selected terminal of the switching circuit; The first control signal includes: a switch control signal and a current control signal; The switching circuit is configured to: turn on the selection terminal coupled between the common terminal and the first light-emitting device according to the switch control signal, so as to couple the current source to the first light-emitting device; The current source is configured to provide a predetermined current to the first light emitting device according to the current control signal.

10. The light emitting device driving circuit according to claim 8, characterized in that: The controller is further configured to output the first control signal corresponding to each light-emitting device to the current driving circuit in sequence according to the voltage of the output end of the voltage conversion circuit corresponding to at least two light-emitting devices from large to small or from small to large.

11. The light emitting device driving circuit according to any one of claims 8 to 10, characterized in that: The voltage conversion circuit includes at least any one of the following: a boost circuit and a buck-boost circuit.

12. A PPG sensor, characterized in that: The device comprises a detector and a light emitting device driving circuit according to any one of claims 1 to 11; wherein the detector is used to detect a test light signal of the light emitting device reflected and / or scattered by a detection object.

13. An electronic device, characterized in that: The method comprises the light-emitting device driving circuit according to any one of claims 1 to 11, or the PPG sensor according to claim 12.

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