Controller for controlling light source module

Abstract

A controller for controlling a light source module is provided. The light source module comprises a first light-emitting diode string and a second light-emitting diode string. The controller comprises a power input terminal for receiving power from the boost converter, a power output terminal for providing electric energy to the light source module via the buck converter, a first input terminal for receiving a first pulse width modulation signal, a second input terminal for receiving a second pulse width modulation signal, and a second input terminal for receiving a second pulse width modulation signal. And a width monitoring terminal for receiving a width monitoring signal. The width monitoring signal indicates a duration of a first state of the first pulse width modulated signal and a duration of a first state of the second pulse width modulated signal. If the width monitoring signal is greater than a width threshold signal, the controller turns off the light source module.

Description

Technical Field

[0001] The present invention relates to the technical field of controllers, and in particular to a controller for controlling a light source module. Background Art

[0002] A driver monitoring system (DMS) is a vehicle safety system that monitors the driver's alertness to help prevent traffic accidents. DMS uses a camera installed in the vehicle's cabin to monitor driver distraction or improper driving behavior and issues an alarm when a problem is detected. To help the camera generate better images, a light source module can be used for illumination. The light source module can include one or more infrared light emitting diode (IR LED) strings. Typically, each LED string is controlled by a controller. To control two LED strings, two controllers are required, which increases cost. When the system is running, the current of the light source module needs to be adjusted within an appropriate range to produce sufficient illumination without causing damage to the human eye. In traditional methods, the current of the light source module is adjusted by changing the resistance of one or more resistors. This traditional method requires the use of resistors with uncommon resistance values ​​or the use of multiple shunt resistors to obtain the desired current, so it has limited flexibility and increases cost. When a traditional controller adjusts the current of the light source module, the rapidly changing current will generate electromagnetic interference (EMI), which may cause other electronic devices in the vehicle to malfunction. In addition, to ensure safe operation of the system, it is necessary to monitor potential short-circuit conditions of the light source module, prevent large surge currents at the controller power terminals, and monitor and control the power consumption of the light source module and controller. Summary of the invention

[0003] The present invention provides a controller for controlling a light source module. The light source module includes a first light emitting diode string and a second light emitting diode string. The controller includes a power input terminal, a power output terminal, a first input terminal, a second input terminal and a width monitoring terminal. The power input terminal is used to receive power from a boost converter. The power output terminal is coupled to the light source module and is used to provide power to the light source module via a buck converter. The first input terminal is used to receive a first pulse width modulation signal, which is used to control a first switch coupled in series with the first light emitting diode string. If the first pulse width modulation signal is in a first state, the first switch is turned on, and if the first pulse width modulation signal is in a second state, the first switch is turned off. The second input terminal is used to receive a second pulse width modulation signal, which is used to control a second switch coupled in series with the second light emitting diode string. If the second pulse width modulation signal is in a first state, the second switch is turned on, and if the second pulse width modulation signal is in a second state, the second switch is turned off. The width monitoring terminal is used to receive a width monitoring signal indicating the duration of the first state of the first pulse width modulation signal and the duration of the first state of the second pulse width modulation signal. If the width monitoring signal is greater than the width threshold signal, the controller turns off the light source module.

[0004] The present invention also provides a controller for controlling a light source module, the light source module includes a first light emitting diode string and a second light emitting diode string. The controller includes a boost control unit for controlling a boost converter, a buck control unit for controlling a buck converter, and a brightness limiting unit. The brightness limiting unit receives a first pulse width modulation signal and a second pulse width modulation signal. The first pulse width modulation signal is used to control a first switch coupled in series with the first light emitting diode string. If the first pulse width modulation signal is in a first state, the first switch is turned on, and if the first pulse width modulation signal is in a second state, the first switch is turned off. The second pulse width modulation signal is used to control a second switch coupled in series with the second light emitting diode string. If the second pulse width modulation signal is in a first state, the second switch is turned on, and if the second pulse width modulation signal is in a second state, the second switch is turned off. If a width monitoring signal indicating a duration of the first state of the first pulse width modulation signal and a duration of the first state of the second pulse width modulation signal is greater than a width threshold signal indicating a width threshold, the brightness limiting unit turns off the light source module. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The purpose, specific structural features and advantages of the present invention may be further understood by describing some embodiments of the present invention and the accompanying drawings as follows.

[0006] Figure 1FIG. 1 is a light source driving circuit for controlling a light source module according to an embodiment of the present invention;

[0007] Figure 2 FIG. 1 is a signal waveform diagram of a light source driving circuit according to an embodiment of the present invention;

[0008] Figure 3 FIG. 1 is a block diagram of a controller for controlling a light source module according to an embodiment of the present invention;

[0009] Figure 4 FIG. 1 is a circuit diagram of a brightness limiting unit of a controller according to an embodiment of the present invention;

[0010] Figure 5 Shown is a circuit diagram of a protection unit of a controller according to an embodiment of the present invention;

[0011] Fig. 6A FIG. 1 is a circuit diagram of a dimming unit of a controller according to an embodiment of the present invention;

[0012] Figure 6B FIG. 1 is a circuit diagram of a dimming unit of a controller according to an embodiment of the present invention;

[0013] Figure 7 Shown is a circuit diagram of a gradual start unit of a controller according to one embodiment of the present invention;

[0014] Figure 8 FIG. 1 is a circuit diagram of an inrush current control unit of a controller according to an embodiment of the present invention;

[0015] Fig. 9 FIG. 4 is a diagram showing a light source driving circuit for controlling a light source module according to an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The following will provide a detailed description of embodiments of the present invention. Although the present invention is described and illustrated by these embodiments, it should be noted that the present invention is not limited to these embodiments. On the contrary, the present invention encompasses all substitutes, variants and equivalents within the spirit of the invention and the scope of the invention as defined by the appended claims.

[0017] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. Those skilled in the art will appreciate that the present invention can be implemented without these specific details. In other examples, well-known methods, processes, components and circuits are not described in detail in order to highlight the subject matter of the present invention.

[0018] Figure 1FIG. 1 is a diagram showing a light source driving circuit 100 for controlling a light source module according to an embodiment of the present invention. The light source driving circuit 100 includes a controller 180 .

[0019] exist Figure 1 In the example of FIG. 1 , the light source module includes two LED strings 101 and 102, wherein each LED string includes a plurality of (e.g., two) LEDs. In one embodiment, the LEDs in the LED strings 101 and 102 are infrared LEDs. This example is used as the basis for the following discussion; however, the present invention is not limited to two LED strings and / or two LEDs per string.

[0020] The controller 180 includes a power input terminal VBUCKIN, a power output terminal LX, a first input terminal, and a second input terminal. The power input terminal VBUCKIN is used to receive power from the boost converter. The power output terminal LX is coupled to the light source module and is used to provide power to the light source module via the buck converter. Figure 1 In the example of FIG. 1 , the boost converter includes an inductor L1, a diode D1, an output capacitor CO1 and a transistor 301 (shown in FIG. Figure 3 The buck converter includes an inductor L2, an output capacitor CO2, and transistors 302 and 303 (shown in FIG. Figure 3 ). The first input terminal DPWMA is used to receive a first pulse width modulation (PWM) signal PWMA. The second input terminal DPWMB is used to receive a second pulse width modulation signal PWMB. In one embodiment, the first pulse width modulation signal PWMA and the second pulse width modulation signal PWMB are provided by an electronic control unit (ECU) of the vehicle. The first pulse width modulation signal PWMA is used to control a first switch Q1 coupled in series with the first LED string 101. If PWMA is in a first state (e.g., logic high), the first switch Q1 is turned on; if PWMA is in a second state (e.g., logic low), the first switch Q1 is turned off. The second pulse width modulation signal PWMB is used to control a second switch Q2 coupled in series with the second LED string 102. If PWMB is in a first state (e.g., logic high), the second switch Q2 is turned on; if PWMB is in a second state (e.g., logic low), the second switch Q2 is turned off. PWMA and PWMB are configured so that the first switch Q1 and the second switch Q2 are not turned on at the same time. As Figure 2As shown, during the time period Tona, PWMA is in the first state, and the switch Q1 is turned on. During the time period Tonb, PWMB is in the first state, and the switch Q2 is turned on. By configuring in this way, the on-time period Tona of the switch Q1 and the on-time period Tonb of the switch Q2 do not overlap each other. In one embodiment, PWMA and PWMB have the same duty cycle and different phases. In other words, in such an embodiment, Tona is equal to Tonb, and the waveform of PWMB is obtained by time-delaying the waveform of PWMA.

[0021] The controller 180 also includes a width monitoring terminal DPWMLIM, a current monitoring terminal ISEN, a first voltage monitoring terminal VS, a second voltage monitoring terminal VSEN_BK, a dimming terminal APWM, a gradual start terminal SST_BK, a power terminal PFETOUT, a third voltage monitoring terminal FB_BST, monitoring terminals ISP and ISN, and a reference voltage terminal VREF.

[0022] The width monitoring terminal DPWMLIM is used to receive a width monitoring signal WID, which indicates the first state duration Tona of the first pulse width modulation signal PWMA and the first state duration Tonb of the second pulse width modulation signal PWMB. If the width monitoring signal WID is greater than the width threshold signal, the controller 180 turns off the light source module. The width monitoring terminal DPWMLIM is coupled to the capacitor CP.

[0023] The current monitoring terminal ISEN is coupled to the monitoring resistor IRSEN. The monitoring resistor IRSEN is coupled to the cathode of the first LED string 101 through the switch Q1, and is coupled to the cathode of the second LED string 102 through the switch Q2. The monitoring terminal ISEN is used to receive a current monitoring signal ISEN1 from the monitoring resistor IRSEN. The current monitoring signal ISEN1 is a voltage across the monitoring resistor IRSEN, which can indicate the magnitude of the current of the first LED string 101 and the magnitude of the current of the second LED string 102. If the switch Q1 is turned on, the current of the first LED string 101 flows from the buck converter through the first LED string 101, the switch Q1 and the monitoring resistor IRSEN to the ground. If the switch Q2 is turned on, the current of the second LED string 102 flows from the buck converter through the second LED string 102, the switch Q2 and the monitoring resistor IRSEN to the ground. Advantageously, the controller 180 can monitor the magnitude of the current of the LED strings 101 and 102 using a single current monitoring terminal ISEN and adjust the current accordingly. Compared with the conventional controller that can only monitor and control one LED string, the controller 180 of the present invention can monitor and control multiple (e.g., two) LED strings. These LED strings can be placed at different locations in the vehicle cabin to provide lighting at different angles, so that the driver monitoring system can better monitor the driver's condition.

[0024] The first voltage monitoring terminal VS is coupled to the anode of the light source module (for example, the anode of the first LED string 101 and the second LED string 102) through the voltage divider 103, and receives a first voltage monitoring signal VS1 indicating the voltage level at the anode of the light source module. The current monitoring signal ISEN1 can indicate the voltage level at the cathode of the light source module. The second voltage monitoring terminal VSEN_BK is coupled to the anode of the light source module, and receives a second voltage monitoring signal VSBK1 indicating the level of the voltage drop across the light source module. The controller 180 detects a short circuit condition based on the first voltage monitoring signal VS1, the second voltage monitoring signal VSBK1 and the current monitoring signal ISEN1, which will be combined with the current monitoring signal ISEN1 to detect the short circuit condition. Figure 5 Further discussion.

[0025] The dimming terminal APWM is used to receive the third pulse width modulation signal APWM1. The controller 180 generates an analog signal ADJ according to the duty cycle of the third pulse width modulation signal APWM1, and can adjust the current of the first LED string 101 and the current of the second LED string 102 by comparing the analog signal ADJ with the current monitoring signal ISEN1. Figure 3 As shown, the controller 180 includes an amplifier 307 for comparing the analog signal ADJ with the current monitoring signal ISEN1 to generate an error signal EA1. The buck control unit 320 can control the buck converter to adjust the current of the first LED string 101 and the current of the second LED string 102 according to the level of the error signal EA1.

[0026] Reference again Figure 1 The gradual start terminal SST_BK is coupled to the capacitor CS and is used to generate a gradual start signal SST1 by charging and discharging the capacitor CS. When the switch Q1 is turned on, if the voltage of the gradual start signal SST1 is less than the error signal EA1, the controller 180 adjusts the current of the first LED string 101 according to the voltage of the gradual start signal SST1. When the switch Q1 is turned off, the controller 180 adjusts the current of the first LED string 101 according to the voltage of the gradual start signal SST1.

[0027] The power terminal PFETOUT is coupled to the output capacitor CO1 of the boost converter and provides a current for charging the output capacitor CO1 , the charging current being regulated according to the voltage at the power input terminal VBUCKIN.

[0028] The third voltage monitoring terminal FB_BST is coupled to the output end of the boost converter through the voltage divider 104, and is used to monitor the level of the output voltage VBSO of the boost converter. Specifically, the third voltage monitoring terminal FB_BST receives a voltage monitoring signal BST1 indicating the level of the output voltage VBSO. The monitoring terminals ISP and ISN are coupled to both ends of the monitoring resistor RS, and are used to monitor the input current IPWR provided by the power supply 150 and received by the controller 180 through the power supply terminal VIN. The monitoring resistor RS is coupled between the power supply 150 and the controller 180. The controller 180 controls the boost converter to adjust the output voltage VBSO to be lower than the voltage threshold, and controls the boost converter to adjust the input current IPWR to be lower than the current threshold. Alternatively, in the case of Fig. 9 In another embodiment shown, a monitoring resistor RS is coupled between a diode D1 of the boost converter and an output capacitor CO1 of the boost converter. Monitoring terminals ISP and ISN coupled to both ends of the monitoring resistor RS are used to monitor the magnitude of the output current IBSO of the boost converter. The controller 180 controls the boost converter to adjust the output voltage VBSO below a voltage threshold, and controls the boost converter to adjust the output current IBSO below a current threshold.

[0029] Figure 3 FIG. 1 is a diagram for controlling a light source module (eg, Figure 1 1 and 102). The controller 180 includes a boost control unit 310, a buck control unit 320, a brightness limiting unit 330, a protection unit 340, a dimming unit 350, a gradual start unit 360, an inrush current control unit 370, and a power limiting unit 380. The boost control unit 310 is used to control the boost converter by controlling the transistor 301. The buck control unit 320 is used to control the buck converter by controlling the transistors 302 and 303. More specifically, the boost control unit 310 adjusts the output current IBSO and the output voltage VBSO of the boost converter by adjusting the duty cycle of the transistor 301. The buck control unit 320 adjusts the output current and the output voltage of the buck converter by controlling the duty cycle of the transistors 302 and 303.

[0030] Figure 44 is a circuit diagram of a brightness limiting unit 330 according to an embodiment of the present invention. The brightness limiting unit 330 includes a NOR gate 401, a switch 402, a comparator 403 and a trigger 404. The NOR gate 401 receives PWMA and PWMB and generates an output signal to control the switch 402. The switch 402 is coupled in parallel with the capacitor CP. If either PWMA or PWMB is in a first state (e.g., logic high), the switch 402 is turned off, and the capacitor CP is charged by the current provided by the reference voltage terminal VREF. If both PWMA and PWMB are in a second state (e.g., logic low), the switch 402 is turned on, and the capacitor CP is discharged. The voltage across the capacitor CP is the width monitoring signal WID, which indicates the duration Tona of the first state of the first pulse width modulation signal PWMA and the duration Tonb of the first state of the second pulse width modulation signal PWMB. The comparator 403 compares the width monitoring signal WID with the width threshold signal VTH_WID indicating the width (i.e., duration) threshold, and outputs the comparison result to the trigger 404. The trigger 404 generates an alarm signal according to the output of the comparator 403. If the width monitoring signal WID is greater than the width threshold signal VTH_WID, the trigger 404 outputs an alarm signal PWM_LIM having a first state (e.g., logic high), and the controller 180 turns off the light source module accordingly. Since PWMA and PWMB are used to control switches Q1 and Q2, the overall brightness of the light source module is proportional to the durations Tona and Tonb. Advantageously, the brightness of the light source module can be limited to a range that is harmless to the human eye.

[0031] Figure 5 FIG. 3 is a circuit diagram of a protection unit 340 according to an embodiment of the present invention. The protection unit 340 detects the light source module (eg, Figure 1The protection unit 340 includes a differential unit 501, a first comparator COMP1, a second comparator COMP2, a third comparator COMP3, an OR gate 502, an AND gate 503 and a timing unit 504. The differential unit 501 is used to generate a differential signal DIF indicating the difference between the first voltage monitoring signal VS1 and the current monitoring signal ISEN1. The first comparator COMP1 is used to compare the differential signal DIF with the first protection threshold VTH1. The second comparator COMP2 is used to compare the current monitoring signal ISEN1 with the second protection threshold VTH2. The third comparator COMP3 is used to compare the second voltage monitoring signal VSBK1 with the third protection threshold VTH3. The OR gate 502 performs a logic OR operation on the output of the first comparator COMP1 and the output of the third comparator COMP3. The AND gate 503 performs a logic AND operation on the output of the OR gate 502 and the output of the second comparator COMP2. The timing unit 504 generates the alarm signal LEDSHORT according to the output of the AND gate 503, the first pulse width modulation signal PWMA, the second pulse width modulation signal PWMB and the predetermined duration TP. During operation, the protection unit 340 monitors whether the current monitoring signal ISEN1 is greater than the second protection threshold VTH2. If the current monitoring signal ISEN1 is greater than the second protection threshold VTH2, the protection unit 340 further monitors whether the differential signal DIF is less than the first protection threshold VTH1 or the second voltage monitoring signal VSBK1 is less than the third protection threshold VTH3. If the differential signal DIF is less than the first protection threshold VTH1, or the second voltage monitoring signal VSBK1 is less than the third protection threshold VTH3, the protection unit 340 uses the timing unit 504 to monitor the duration of this state. If the duration of this state is greater than the predetermined duration TP, the timing unit 504 generates an alarm signal LEDSHORT indicating that a short circuit condition has occurred, and the controller 180 may shut down the light source module accordingly.

[0032] Fig. 6AFIG. 6 is a circuit diagram of a dimming unit 350 according to an embodiment of the present invention. The dimming unit 350 includes a capacitor C1 that generates an analog signal ADJ according to a duty cycle of a third pulse width modulation signal APWM1. If APWM1 is in a first state, the capacitor C1 is charged; if APWM1 is in a second state, the capacitor C1 is discharged. More specifically, an inverter 602 generates an inverted pulse width modulation signal APWM2 according to the third pulse width modulation signal APWM1. The third pulse width modulation signal APWM1 controls a switch SW1 coupled between a current source 601 and the capacitor C1. The inverted pulse width modulation signal APWM2 controls a switch SW2 coupled in parallel with the capacitor C1. If APWM1 is in a first state (e.g., logic high), the switch SW1 is turned on, the switch SW2 is turned off, and the capacitor C1 is charged by the current from the current source 601. If APWM1 is in a second state (e.g., logic low), the switch SW2 is turned on, the switch SW1 is turned off, and the capacitor C1 is discharged. The voltage on the capacitor C1 is the analog signal ADJ. The level of the analog signal ADJ is proportional to the duty cycle of the third pulse width modulation signal APWM1 . The controller 180 can adjust the current of the first LED string 101 and the current of the second LED string 102 by comparing the analog signal ADJ with the current monitoring signal ISEN1 .

[0033] like Figure 3 As shown, the controller 180 includes an amplifier 307 for comparing the analog signal ADJ with the current monitoring signal ISEN1 to generate an error signal EA1. The error signal EA1 is transmitted to the buck control unit 320 via the multiplexer 390. The buck control unit 320 can adjust the current of the first LED string 101 and the current of the second LED string 102 according to the duty cycle of the transistors 302 and 303 according to the voltage of the error signal EA1. Advantageously, the brightness of the light source module can be adjusted by the third pulse width modulation signal APWM1, so the resistance value of the monitoring resistor IRSEN coupled to the current sensing terminal ISEN can be set to be fixed or can be selected from several standard resistance values, thereby reducing the manufacturing cost.

[0034] Figure 6B 1 shows another embodiment of the dimming unit 350. In this embodiment, the controller 180 further includes a current setting terminal ISET (shown in FIG. 1 ) for receiving a setting signal ISET1. Figure 1). The setting signal ISET1 is generated by the voltage divider 603 according to the voltage of the reference voltage signal VREF1 provided by the reference voltage terminal VREF. The dimming unit 350 includes an amplifier 604 for generating a charging current for the capacitor C1 according to the voltage of the setting signal ISET1. This embodiment can further adjust the analog signal ADJ by changing the resistance ratio of the voltage divider 603. Therefore, the brightness of the light source module can be further adjusted by configuring the voltage divider 603. Advantageously, the controller 180 according to the present invention can meet different application requirements (for example, it can be applicable to light source modules with different types or different numbers of LEDs).

[0035] Figure 7 FIG. 1 is a circuit diagram of a gradual start unit 360 according to an embodiment of the present invention. The gradual start unit 360 generates a gradual start signal SST1 by charging and discharging the second capacitor CS, wherein the gradual start signal SST1 is the voltage on the second capacitor CS. The gradual start unit 360 includes a discharge unit 702, a comparator COMP4, a trigger 706, and an OR gate 703. The discharge unit 702 generates a discharge control signal DSC according to the first pulse width modulation signal PWMA and the second pulse width modulation signal PWMB. In one embodiment, the discharge unit 702 includes an OR gate 704 that performs a logic OR operation on PWMA and PWMB to generate a signal PWMAB, and an inverter 705 that generates a discharge control signal DSC according to the signal PWMAB. The discharge control signal DSC can be used to turn on a switch 714 connected in parallel with the capacitor CS to discharge the capacitor CS. The comparator COMP4 compares the error signal EA1 with the gradual start signal SST1. The R terminal of the trigger 706 receives the output of the comparator COMP4, and generates a charging control signal CHG at the Q terminal according to the output of the comparator COMP4. The charging control signal CHG is used to turn on the switch 713 coupled between the capacitor CS and the power supply 701 to charge the capacitor CS. In one embodiment, the power supply 701 is provided by the reference voltage terminal VREF (see Figure 1 , 4 The OR gate 703 generates a selection signal SEL according to the charge control signal CHG and the discharge control signal DSC.

[0036] like Figure 3As shown, the controller 180 further includes a multiplexer 390 for selectively transmitting the error signal EA1 and the gradual start signal SST1 to the buck control unit 320 according to the selection signal SEL. During operation, when the first switch Q1 is turned on, if the voltage of the gradual start signal SST1 is less than the error signal EA1, the multiplexer 390 selectively transmits the gradual start signal SST1 to the buck control unit 320 according to the selection signal SEL, and the buck control unit 320 adjusts the current of the first LED string 101 according to the voltage of the gradual start signal SST1. When the first switch Q1 is turned off, the multiplexer 390 selectively transmits the gradual start signal SST1 to the buck control unit 320 according to the selection signal SEL, and the buck control unit 320 adjusts the current of the first LED string 101 according to the voltage of the gradual start signal SST1. As a result, when the first switch Q1 is turned on or off, the current of the first LED string 101 changes gradually. Similarly, for the second LED string 102, when the second switch Q2 is turned on or off, the current of the second LED string 102 also changes gradually, so as to reduce electromagnetic interference (EMI) caused by rapid changes in the current of the LED strings 101 and 102.

[0037] Figure 8FIG. 1 is a circuit diagram of an inrush current control unit 370 according to an embodiment of the present invention. The inrush current control unit 370 includes a comparator COMP5, a comparator COMP6, a selection unit 820, a current monitoring unit 810, and an error amplifier EA_CHG. In the startup phase of the boost converter, the power terminal PFETOUT provides a current ICH for charging the output capacitor CO1 of the boost converter, and the inrush current control unit 370 adjusts the current ICH according to the voltage value of the output voltage VBSO of the boost converter. During operation, the comparator COMP5 compares the output voltage VBSO of the boost converter with a first threshold VTH1, and the comparator COMP6 compares the output voltage VBSO of the boost converter with a second threshold VTH2. In one embodiment, the first threshold VTH1 and the second threshold VTH2 are proportional to the voltage VIN1 at the power terminal VIN, and VTH1 is less than VTH2. In one embodiment, VTH1 is equal to 0.8*VIN1, and VTH2 is equal to 0.4*VIN1. The selection unit 820 selects a reference signal from a plurality of reference signals REF1, REF2 and REF3 according to the output of the comparator COMP5 and the output of the comparator COMP6, wherein REF1 is less than REF2 and REF2 is less than REF3. In one embodiment, if VBSO is less than VTH1, the selection unit 802 selects REF1; if VBSO is greater than VTH1 and less than VTH2, the selection unit 820 selects REF2; and if VBSO is greater than VTH2, the selection unit 820 selects REF3. The current monitoring unit 810 generates a monitoring signal SENSE indicating the magnitude of the current ICH. The error amplifier EA_CHG controls the transistor 803 coupled in series with the output capacitor CO1 according to the monitoring signal SENSE and the reference signal selected by the selection unit 820 to adjust the magnitude of the current ICH. As described above, in the startup phase, the surge current control unit 370 adjusts the current ICH to different values ​​according to the output voltage VBSO of the boost converter. Advantageously, the output capacitor CO1 can be charged relatively quickly without receiving too much surge current from the power terminal VIN, so that excessive power consumption or excessive temperature will not occur.

[0038] refer to Figure 1 and Figure 3, the controller 180 includes a power limiting unit 380. The power limiting unit 380 controls the boost converter to adjust the output voltage VBSO of the boost converter to be lower than the voltage threshold, and controls the boost converter to adjust the input current IPWR received by the controller 180 from the power supply 150 to be less than the current threshold. The power limiting unit 380 includes a first error amplifier EA_V, a second error amplifier EA_I, and a selection unit 381. The first error amplifier EA_V compares a voltage monitoring signal BST1 indicating the level of the output voltage VBSO of the boost converter with a first threshold signal V1 indicating a voltage threshold (e.g., 2V). The second error amplifier EA_I compares a current monitoring signal ISEN2 indicating the magnitude of the input current IPWR with a second threshold signal V2 indicating a current threshold. The current monitoring signal ISEN2 is generated by the amplifier 382 according to the monitoring signals ISP1 and ISN1 received by the monitoring terminals ISP and ISN.

[0039] refer to Figure 1 , the monitoring terminals ISP and ISN are coupled to the two ends of the monitoring resistor RS respectively. Figure 1 In the example of , the monitoring resistor RS is coupled between the power supply 150 and the controller 180, and the current monitoring signal ISEN2 indicates the amplitude of the input current IPWR flowing from the power supply 150 to the controller 180. The selection unit 381 selectively transmits the output of the first error amplifier EA_V and the output of the second error amplifier EA_I to the boost control unit 310. During operation, if the output voltage VBSO of the boost converter is greater than the voltage threshold (e.g., 2V), the selection unit 381 selectively transmits the output of the first error amplifier EA_V to the boost control unit 310. Accordingly, the boost control unit 310 adjusts the output voltage VBSO to be lower than the voltage threshold. If the output voltage VBSO of the boost converter is less than the voltage threshold, the selection unit 381 selectively transmits the output of the second error amplifier EA_I to the boost control unit 310. Accordingly, the boost control unit 310 adjusts the input current IPWR to be lower than the current threshold. Advantageously, the power consumption of the light source driving circuit 100 including the controller 180 and the light source module can be monitored and controlled within a desired range, thereby protecting the power source 150 (eg, a battery) from being over-discharged.

[0040] In another embodiment, the power limiting unit 380 controls the boost converter to adjust the output voltage VBSO of the boost converter to be lower than the voltage threshold, and controls the boost converter to adjust the output current IBSO of the boost converter to be lower than the current threshold. Fig. 9As shown, the monitoring resistor RS is coupled between the boost converter diode D1 and the boost converter output capacitor CO1 to monitor the magnitude of the boost converter output current IBSO. In this configuration, the reference Figure 3 , the current monitoring signal ISEN2 indicates the magnitude of the output current IBSO. During operation, if the output voltage VBSO of the boost converter is greater than a voltage threshold (e.g., 2V), the selection unit 381 selectively transmits the output of the first error amplifier EA_V to the boost control unit 310. Accordingly, the boost control unit 310 adjusts the output voltage VBSO to be lower than the voltage threshold. If the output voltage VBSO of the boost converter is less than the voltage threshold, the selection unit 381 selectively transmits the output of the second error amplifier EA_I to the boost control unit 310. Accordingly, the boost control unit 310 adjusts the output current IBSO to be lower than the current threshold.

[0041] The above specific implementation methods and drawings are only common embodiments of the present invention. Obviously, various additions, modifications and substitutions can be made without departing from the spirit and scope of the present invention defined by the claims. It should be understood by those skilled in the art that the present invention can be varied in form, structure, layout, proportion, material, element, assembly and other aspects according to specific environment and working requirements in practical applications without departing from the invention criteria. Therefore, the embodiments disclosed herein are only for illustration and not limitation, and the scope of the present invention is defined by the attached claims and their legal equivalents, and is not limited to the previous description.

Claims

1. A controller for controlling a light source module, wherein the light source module comprises a first light emitting diode string and a second light emitting diode string, characterized in that: The controller comprises: a power input terminal for receiving power from the boost converter; a power output terminal, coupled to the light source module, for providing the power to the light source module via a step-down converter; A first input terminal is used to receive a first pulse width modulation signal, wherein the first pulse width modulation signal is used to control a first switch coupled in series with the first light emitting diode string, if the first pulse width modulation signal is in a first state, the first switch is turned on, if the first pulse width modulation signal is in a second state, the first switch is turned off; a second input terminal for receiving a second pulse width modulation signal, wherein the second pulse width modulation signal is used to control a second switch coupled in series with the second light-emitting diode string, wherein if the second pulse width modulation signal is in a first state, the second switch is turned on, and if the second pulse width modulation signal is in a second state, the second switch is turned off; and a width monitoring terminal for receiving a width monitoring signal indicating a duration of a first state of the first pulse width modulation signal and a duration of a first state of the second pulse width modulation signal, If the width monitoring signal is greater than a width threshold signal, the controller turns off the light source module.

2. The controller according to claim 1, characterized in that: The controller further comprises: a current monitoring terminal coupled to a monitoring resistor, wherein the monitoring resistor is coupled to a cathode of the first LED string through the first switch and is coupled to a cathode of the second LED string through the second switch, the current monitoring terminal is used to receive a current monitoring signal from the monitoring resistor, the current monitoring signal indicating a current of the first LED string and a current of the second LED string, Wherein, if the first switch is turned on, the current of the first LED string flows from the buck converter through the first LED string, the first switch and the monitoring resistor to the ground; if the second switch is turned on, the current of the second LED string flows from the buck converter through the second LED string, the second switch and the monitoring resistor to the ground.

3. The controller according to claim 2, characterized in that: The controller further comprises: a first voltage monitoring terminal coupled to the anode of the light source module via a voltage divider, and configured to receive a first voltage monitoring signal indicating a voltage at the anode of the light source module; and A second voltage monitoring terminal is coupled to the anode of the light source module and is used to receive a second voltage monitoring signal indicating a voltage drop across the light source module. The controller detects a short circuit state according to the first voltage monitoring signal, the second voltage monitoring signal and the current monitoring signal.

4. The controller according to claim 2, characterized in that: The controller further comprises: The dimming terminal is used to receive a third pulse width modulation signal. The controller generates an analog signal according to the third pulse width modulation signal, and adjusts the current of the first light emitting diode string and the current of the second light emitting diode string by comparing the analog signal with the current monitoring signal.

5. The controller according to claim 4, characterized in that: The controller further comprises: an amplifier for comparing the analog signal and the current monitoring signal to generate an error signal; a gradual start terminal coupled to the capacitor and configured to generate a gradual start signal by charging and discharging the capacitor, Wherein, when the first switch is turned on, if the voltage of the gradual start signal is less than the error signal, the controller adjusts the current of the first light-emitting diode string according to the gradual start signal, When the first switch is turned off, the controller adjusts the current of the first light emitting diode string according to the gradual start signal.

6. The controller according to claim 1, characterized in that: The controller further comprises: A power terminal is coupled to the output capacitor of the boost converter and is used to provide a current for charging the output capacitor, wherein the current is regulated according to the voltage at the power input terminal.

7. The controller according to claim 1, characterized in that: The controller further comprises: a voltage monitoring terminal, coupled to the output of the boost converter via a voltage divider, for monitoring the output voltage of the boost converter; The first monitoring terminal and the second monitoring terminal are coupled to the monitoring resistor and are used to monitor the input current received by the controller from the power supply. The monitoring resistor is coupled between the power supply and the controller, and the controller controls the boost converter to adjust the output voltage to be lower than a voltage threshold, and controls the boost converter to adjust the input current to be lower than a current threshold.

8. The controller according to claim 1, characterized in that: The controller further comprises: a voltage monitoring terminal, coupled to the output of the boost converter via a voltage divider, for monitoring the output voltage of the boost converter; The first monitoring terminal and the second monitoring terminal are coupled with the monitoring resistor and are used to monitor the output current of the boost converter. The monitoring resistor is coupled between the diode of the boost converter and the output capacitor of the boost converter, and the controller controls the boost converter to adjust the output voltage to be lower than a voltage threshold, and controls the boost converter to adjust the output current to be lower than a current threshold.

9. A controller for controlling a light source module, the light source module comprising a first light emitting diode string and a second light emitting diode string, characterized in that: The controller comprises: A boost control unit, used for controlling the boost converter; a buck control unit for controlling the buck converter; and The brightness limiting unit is used to receive the first pulse width modulation signal and the second pulse width modulation signal, wherein: The first pulse width modulation signal is used to control a first switch coupled in series with the first light emitting diode string. If the first pulse width modulation signal is in a first state, the first switch is turned on. If the first pulse width modulation signal is in a second state, the first switch is turned off. The second pulse width modulation signal is used to control a second switch coupled in series with the second light emitting diode string. If the second pulse width modulation signal is in a first state, the second switch is turned on. If the second pulse width modulation signal is in a second state, the second switch is turned off. If the width monitoring signal indicating the duration of the first state of the first pulse width modulation signal and the duration of the first state of the second pulse width modulation signal is greater than a width threshold signal indicating a width threshold, the brightness limiting unit turns off the light source module.

10. The controller according to claim 9, characterized in that: The brightness limiting unit comprises: a switch coupled in parallel with the capacitor, wherein if the first pulse width modulation signal is in a first state or the second pulse width modulation signal is in a first state, the switch is turned off to charge the capacitor, and if both the first pulse width modulation signal and the second pulse width modulation signal are in a second state, the switch is turned on to discharge the capacitor, wherein the width monitoring signal is a voltage across the capacitor; a comparator for comparing the width monitoring signal with the width threshold signal; and A trigger is used to generate an alarm signal according to the output of the comparator.

11. The controller according to claim 9, characterized in that: The controller further comprises: a current monitoring terminal coupled to a monitoring resistor, for receiving a current monitoring signal indicating a current of the first LED string and a current of the second LED string, wherein the monitoring resistor is coupled to a cathode of the first LED string and a cathode of the second LED string, The current of the first LED string flows from the buck converter through the first LED string, the first switch and the monitoring resistor to the ground, and the current of the second LED string flows from the buck converter through the second LED string, the second switch and the monitoring resistor to the ground.

12. The controller according to claim 11, characterized in that: The controller further comprises: a protection unit, configured to detect a short circuit condition according to the first voltage monitoring signal, the second voltage monitoring signal and the current monitoring signal, The first voltage monitoring signal indicates the voltage at the anode of the light source module, the second voltage monitoring signal indicates the voltage drop across the light source module, and the current monitoring signal further indicates the voltage at the cathode of the light source module. Wherein, the protection unit comprises: a differential unit, configured to generate a differential signal indicating a difference between the first voltage monitoring signal and the current monitoring signal; A first comparator, used for comparing the differential signal with a first protection threshold; A second comparator, used for comparing the current monitoring signal with a second protection threshold; A third comparator, used for comparing the second voltage monitoring signal with a third protection threshold; an OR gate, configured to perform a logic OR operation on an output of the first comparator and an output of the third comparator; an AND gate for performing a logic AND operation on an output of the OR gate and an output of the second comparator; and A timing unit is used to generate an alarm signal according to the output of the AND gate, the first pulse width modulation signal, the second pulse width modulation signal and a predetermined duration.

13. The controller according to claim 11, characterized in that: The controller further comprises: A dimming unit, the dimming unit comprising: a first capacitor, used to generate an analog signal according to a third pulse width modulation signal, wherein if the third pulse width modulation signal is in a first state, the first capacitor is charged, and if the third pulse width modulation signal is in a second state, the first capacitor is discharged, wherein the level of the analog signal is proportional to the duty cycle of the third pulse width modulation signal, The controller adjusts the current of the first LED string and the current of the second LED string by comparing the analog signal with the current monitoring signal.

14. The controller according to claim 13, characterized in that: The dimming unit also includes: an amplifier, configured to generate a current for charging the first capacitor according to a setting signal, The setting signal is generated by a voltage divider according to a reference voltage signal provided by a reference voltage terminal of the controller.

15. The controller according to claim 13, characterized in that: The controller further comprises: an amplifier for comparing the analog signal and the current monitoring signal to generate an error signal; A gradual start-up unit, configured to generate a gradual start-up signal by charging and discharging a second capacitor, wherein the gradual start-up signal is a voltage on the second capacitor, and the gradual start-up unit comprises: a discharge unit, configured to generate a discharge control signal according to the first pulse width modulation signal and the second pulse width modulation signal; a comparator for comparing the error signal with the progressive start signal; a trigger, configured to generate a charging control signal according to an output of the comparator; and an OR gate, used to generate a selection signal according to the charging control signal and the discharging control signal, The charging control signal is used to turn on the third switch to charge the second capacitor, and the discharging control signal is used to turn on the fourth switch to discharge the second capacitor. The controller further comprises a multiplexer, and the multiplexer is used to selectively transmit the error signal and the gradual start signal to the step-down control unit according to the selection signal. Wherein, when the first switch is turned on, if the voltage of the gradual start signal is less than the error signal, the step-down control unit adjusts the current of the first light-emitting diode string according to the gradual start signal, When the first switch is disconnected, the voltage reduction control unit adjusts the current of the first light emitting diode string according to the gradual start signal.

16. The controller according to claim 9, characterized in that: The controller further comprises: a power terminal coupled to an output capacitor of the boost converter and configured to provide a current for charging the output capacitor; An inrush current control unit, configured to adjust the current according to the output voltage of the boost converter, wherein the inrush current control unit comprises: A first comparator, configured to compare the output voltage of the boost converter with a first threshold; a second comparator, configured to compare the output voltage of the boost converter with a second threshold; a selection unit, configured to select a reference signal from a plurality of reference signals according to an output of the first comparator and an output of the second comparator; a current monitoring unit, configured to generate a monitoring signal indicative of the current; and An error amplifier is used to control a transistor coupled in series with the output capacitor according to the monitoring signal and a reference signal selected by the selection unit to adjust the current.

17. The controller according to claim 9, characterized in that: The controller further comprises: a power limiting unit for controlling the boost converter to adjust the output voltage of the boost converter to be below a voltage threshold, and controlling the boost converter to adjust the input current received by the controller from a power source to be below a current threshold, wherein the power limiting unit comprises: a first error amplifier for comparing a voltage monitoring signal indicative of an output voltage of the boost converter with a first threshold signal indicative of the voltage threshold; a second error amplifier for comparing a current monitoring signal indicative of the input current with a second threshold signal indicative of the current threshold; and The selection unit is used for selectively transmitting the output of the first error amplifier and the output of the second error amplifier to the boost control unit.

18. The controller according to claim 9, characterized in that The controller further comprises: a power limiting unit, configured to control the boost converter to adjust the output voltage of the boost converter to be lower than a voltage threshold, and to control the boost converter to adjust the output current of the boost converter to be lower than a current threshold, wherein the power limiting unit comprises: a first error amplifier, configured to compare a voltage monitoring signal indicating the output voltage with a first threshold signal indicating the voltage threshold; a second error amplifier, configured to compare a current monitoring signal indicative of the output current with a second threshold signal indicative of the current threshold; and The selection unit is used for selectively transmitting the output of the first error amplifier and the output of the second error amplifier to the boost control unit.

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