Abstract:
A single integrated circuit includes a single boost converter, a first circuit, a second circuit, and a controller. The single boost converter supplies power to the first and second circuits. The controller receives an operational mode signal and in response to the operational mode signal, drives the single boost converter to respectively provide power to the first and second circuits. When the first and second circuits are simultaneously active, the controller manages an operation of the first circuit so that proper operation of the second circuit is maintained. The first circuit may be an LED flash driver, and the second circuit may be an audio amplifier, such as a Class-D audio amplifier. The controller manages an operation of the audio amplifier so that a sufficient amount of current is supplied to the LED flash driver for proper operation of the LED flash driver.

Description:
The present invention claims priority to U.S. provisional patent application Ser. No. 61/508,435, filed 15 Jul. 2011 and is incorporated by reference in its entirety. 
    
    
     FIELD OF INVENTION 
     The present invention generally relates to an integrated circuit, and, more particularly, to using a single boost converter in a single integrated circuit that supplies power to two or more separate operational or functional circuits in the single integrated circuit. 
     BACKGROUND OF THE INVENTION 
     Many mobile phones on the market today provide phone functionality and also have a built in camera with flash capability in order to take higher quality photos. These phones require circuitry that enables audio functionality for the phone and the flash capability. Audio functionality for a mobile phone is not just limited to the phone functionality but can also include the audio functionality for playing music, games, and videos and running applications and programs. 
     The camera flashes on mobile phones use light emitting diode (LED) flash drivers to enable flash capability. The majority of these flashes for mobile phones are enabled through a boosted LED flash driver (e.g., having a boost converter). The boost converter is used for powering the LED driver and works to provide a constant current source. The output voltage of the boost converter changes with the forward voltage drop of the LED flash driver because the LED flash driver needs a constant current with a threshold forward voltage applied in order to enable it. The LED flash driver will require a certain power to operate as the battery voltage decreases over time to maintain flash capability, and therefore a boost converter is required. The typical forward voltage drop of the LED flash to enable the LED flash drivers is between 2.6 Volts and 3.8 Volts, and the boost voltage will vary according to the typical forward voltage drop.  FIG. 1  shows a forward current versus forward voltage plot diagram for an exemplary LED flash driver in accordance with the prior art that is disclosed in Phillips Lumileds Lighting Company Technical Datasheet DS49 for LUXEON Flash dated October 2006. Generally, the flash driver uses a boost converter that works as a constant current source wherein the flash driver is enabled using hardware pins and configurable via an I 2 C interface. Such an exemplary LED flash driver is disclosed in Analogic Tech Product Datasheet AAT 1271 for 1.5 A Step-Up Current Regulator for Flash LED dated April 2009. 
     Also, mobile phones on the market today use a boosted audio amplifier for a more efficient system and for higher and louder audio quality. A boosted audio amplifier comprises a boost converter powering an audio amplifier. By boosting the audio amplifier, the sound output of the amplifier will be increased and louder. In addition, by boosting the voltage to a higher voltage level, the sound output will no longer be clipped by the battery voltage threshold because the audio amplifier is not limited to the voltage supplied by the battery. 
     Different types of audio amplifiers exist. Such types of amplifiers include but are not limited to Class D, H, A, B, and A-B amplifiers. A boosted class-D amplifier can deliver a higher output power independent of the battery voltage because the boost can guarantee constant deliverance of power into the audio amplifier. When a boost converter is used for powering a class-D amplifier, the boost converter works to provide a constant voltage source to the audio amplifier. In another case, a class-H scheme is implemented to maximize the boost converter efficiency by varying the boost output voltage at a certain signal level. At each respective signal level, the boost converter works to provide a corresponding constant voltage source. One disadvantage of the powering scheme for a boosted Class-D amplifier is that the overall system cost and size increase due to the requirements of additional components related to operating the boost converter with the audio amplifier. 
     Since both the LED flash driver and the audio amplifier require a similar or same type of boost converter, there is a desire and need for both the LED flash driver and audio amplifier to be supplied by a single boost converter. 
       FIG. 2  depicts an exemplary block diagram of an LED flash driver and audio amplifier power supply in accordance with the prior art in which a single boost converter is used to simultaneously drive both the LED flash driver and audio amplifier power supply. Such an exemplary circuit implementation is disclosed in Texas Instruments Datasheet for TPS61300, TPS61301, TPS61305 entitled “1.5 A/4.1 A Multiple LED Camera Flash Driver with I2CTM Compatible Interface” dated June 2009 and revised September 2010. Referring to  FIG. 2 , a constant DC voltage supply  102  is coupled to a capacitor  104  and an inductor  106 . Moreover, the inductor  106  is coupled to an integrated circuit (“IC”)  108  that comprises a single boosted LED driver and controller. The boosted LED flash driver IC  108  drives the LED flash light using another capacitor  110  and diodes  112 , 114 . The LED flash driver IC  108  also drives an audio amplifier  124 . The audio amplifier  124  comprises a Class-D amplifier  120 , two audio inputs  116 , 118  and a speaker system  122  that outputs an audio signal. Control of LED flash driver IC  108  and audio amplifier  124  is provided at the board level. Such control at the board level can be provided through system software that uses a General Purpose Input/Output (GPIO) port of the LED flash driver IC  108 , or an I 2 C interface. Such control may involve the exclusive operation of either the LED flash driver IC  108  or audio amplifier  124 , or operating the LED flash driver IC  108  and the audio amplifier  124  simultaneously. When operating simultaneously, the control includes reducing the gain of the audio amplifier  124 . Since the audio amplifier  124  is external to the controller in LED flash driver IC  108 , the audio signal level is not monitored before the LED flash is turned on. Thus, the gain amount of the audio signal that needs to be attenuated is hard to determine, and in most cases, due to the high crest factor of music contents, a need to reduce audio gain may not even exist. Thus, the controller for the LED flash driver  108  is limited to being used to control the audio amplifier  124 . Therefore, it is desirable to provide a way to control both the LED flash driver and the audio amplifier by using a controller that is on a single integrated circuit. 
     SUMMARY OF THE INVENTION 
     The above stated objective of using a single boost converter in a single integrated circuit that supplies power to two or more separate operational or functional circuits in the single integrated circuit is accomplished in a single integrated circuit and a method. The method is a method of driving a first circuit and a second circuit using a single boost converter that are all within the single integrated circuit. 
     The single integrated circuit includes a single boost converter, a first circuit, a second circuit, and a controller. The single boost converter supplies power. The first circuit provides a circuit operation and is coupled to the single boost converter that supplies power to the first circuit. The second circuit provides another circuit operation and is coupled to the single boost converter that supplies power to the second circuit. The controller is coupled to the single boost converter, the first circuit, and the second circuit. The controller receives an operational mode signal and in response to the operational mode signal, drives the single boost converter to respectively provide power to the first circuit and the second circuit. 
     The controller may be a single controller. When the first and second circuits are simultaneously active, the controller manages an operation of the first circuit so that proper operation of the second circuit is maintained. In one embodiment, the first circuit may be an LED flash driver, and the second circuit may be an audio amplifier, such as a Class-D audio amplifier. The controller manages an operation of the audio amplifier so that a sufficient amount of current is supplied to the LED flash driver for proper operation of the LED flash driver. One way of the controller managing the operation of the audio amplifier is by maintaining the power through the audio amplifier within a power amplitude limit. Another way of the controller managing the operation of the audio amplifier is by mapping power between the audio amplifier and the LED flash driver based on a total amount of power provided by the single boost converter. A further way of the controller managing the operation of the audio amplifier is by maintaining the power through the audio amplifier within a power amplitude limit. A still further way of the controller managing the operation of the audio amplifier is by lowering a volume signal of the audio amplifier to ensure that the sufficient amount of current is supplied to the LED flash driver for proper operation of the LED flash driver. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plot diagram showing the forward current versus forward voltage relationship for an exemplary LED flash driver in accordance with the prior art. 
         FIG. 2  is an exemplary block diagram of an LED flash driver and audio amplifier power supply in accordance with the prior art in which a single boost converter is used to simultaneously drive both the LED flash driver and audio amplifier power supply. 
         FIG. 3  is an exemplary block diagram of a single integrated circuit that uses a single boost converter in the single integrated circuit that supplies power to two or more separate operational or functional circuits, such as an LED flash driver and an audio amplifier, in the single integrated circuit. 
         FIG. 4  is a more detailed exemplary block diagram of an LED flash driver to which the single boost converter in the single integrated circuit supplies power. 
         FIG. 5  is an exemplary timing diagram for a signal of the single integrated circuit that signifies whether the LED flash is on and being used or whether the audio amplifier is on and being used. 
         FIG. 6  is a plot diagram showing a power versus time relationship for the LED flash driver and the audio amplifier in which the single integrated circuit is operating in a mode such that operation of both the LED flash and the audio amplifier does not exceed a power threshold limit. 
         FIG. 7  is a plot diagram showing a power versus time relationship for the LED flash driver and the audio amplifier in which the single integrated circuit is operating in a mode such that operation of both the LED flash and the audio amplifier does exceed a power threshold limit. 
         FIG. 8  is an exemplary chart showing the mapping of power supplied to the LED flash driver and the audio amplifier. 
         FIG. 9  is an exemplary timing diagram of various signals for the single integrated circuit when the LED flash is turned on at higher audio signals of the audio amplifier. 
         FIG. 10  is an exemplary state diagram of an algorithm for the controller shown in  FIGS. 3 and 4 . 
     
    
    
     DETAILED DESCRIPTION 
     A single integrated circuit (“IC’)  200  has a single boost converter  202  that is used to supply power to two or more separate operational or functional circuits in the IC  200 .  FIG. 3  shows an exemplary block diagram of the IC  200  with a boosted audio class D amplifier  206  and an integrated LED flash driver  204 . The LED flash driver  204  can be a first circuit that provides LED flash driver circuit operations, and the audio amplifier  206  can be a second circuit that provides audio amplification circuit operations. The single IC  200  comprises a controller  208  that is coupled to a single boost converter  202 , LED flash driver  204 , and audio amplifier  206 . The single boost converter  202  is able to drive both the LED flash driver  204  and audio amplifier  206 , wherein the LED flash driver  204  requires a constant current in order to drive the LED flash and the audio amplifier  206  requires a constant voltage to operate. The controller  208  is coupled to all three blocks on the single integrated circuit  200  that enables both LED flash and audio capability. Controller  208  receives an external operational mode signal(s), such as is_flash_on signal  211  (i.e., LED flash on signal), is_movie_on signal  212  (i.e., Movie on signal), and is_audio_on signal  214  (i.e., Audio on signal). In  FIG. 3 , the LED flash driver  204  is supplied with boosted power from the boost converter  202  that is set by the controller  208  in order to maintain constant current for the LED flash driver  204  to operate its flash capability.  FIG. 4  shows a more detailed exemplary block diagram of the LED flash driver  204 . The LED flash driver  204  receives a control input signal  216  from the controller  208  and sends the control input signal  216  from the controller  208  to the current source  218 . The current source  218  is able to adjust and set the current accordingly using the ratio systematic implementation of two field effect transistors (“FETs”). Once the current has been adjusted to drive the LED flash diode  226 , a real time voltage at the output of the LED flash diode  226  is fed back to the controller  208  through feedback voltage signal  228 . This real time feedback voltage signal  228  factors in and accounts for different forward voltage drops of the flash being used (e.g., the forward voltage drops of the LED flash diode  226 ). The controller  208  provides thermal management of the flash operation by adjusting the constant current provided to the LED flash driver  204  in accordance with different working conditions of the flash. This thermal management of flash operations ensures that the amount of power dissipated in the die is minimized or reduced. 
     As shown in  FIG. 3 , the audio Class D amplifier  206  is supplied with boosted power from the boost converter  202  that is set by the controller  208  in order to maintain constant voltage for the audio amplifier  206  to maintain operations. 
     The IC  200  has two modes of operation: an LED flash mode and audio amplifier mode. The LED flash mode is when the flash capability is turned on, and the audio amplifier mode is when the audio capability is turned on.  FIG. 5  shows an exemplary timing diagram of an is_flash_on signal  211 . The high values of the is_flash_on signal  211  connote when LED flash is on and being used (e.g., in LED flash mode) while the low values of is_flash_on signal  211  connote when the audio amplifier  206  is on and being used (e.g., audio amplifier mode). This operational mode signal is, but is not limited to, a square wave signal. 
     In the LED flash mode, there are two LED flash driver modes of operation for driving constant current to the LED flash driver  204 . The first LED flash driver mode is a camera mode in which the constant current applied to the LED flash driver  204  is a high current value. The second LED flash driver mode is a movie mode in which the constant current applied to the LED flash driver  204  is a low current value. When the LED flash driver  204  is on, an is_camera_on signal provides an indication to the controller  208  that the LED flash driver mode is in camera mode. When both the camera and movie mode are on, the camera mode overrides the movie mode and provides an indication to the controller  208  that the camera mode is on, or otherwise provides an indication to the controller  208  that the LED flash driver mode is in the movie mode. 
     IC  200  driving the LED flash driver  204  and the audio amplifier  206  is not limited in any particular ways for operating and/or configurations as various ways for operating and different configurations for IC  200  exist, including but not limited to the ones disclosed in this detailed description. The is_audio_on signal  214  is the signal that indicates to the controller  208  when the audio amplifier  206  is to be turned on irrespective of the mode of operation or the LED flash driver mode for IC  200 . 
     A first exemplary IC operating configuration is when the audio class D amplifier  206  is on and the LED flash driver  204  is completely off (e.g., when the is_audio_on signal  214  is on and IC  200  is in audio amplifier mode) or when the audio class D amplifier  206  is completely off and the LED flash driver  204  is on (e.g., when the is_flash_on signal  211  is on and the IC  200  is in LED flash mode). For the first exemplary IC operating configuration, the is_flash_on signal  211  is the signal that indicates to controller  208  when the flash is turned on, and the is_audio_on signal  214  is the signal that indicates to controller  208  to turn on the audio amplifier  206 . However, in one implementation, when is_flash_on signal  211  is on and the flash is turned on, the controller  208  ensures that audio amplifier  206  is off, despite whether is_audio_on signal  214  is on. 
     A second exemplary IC operation configuration is when both the audio class D amplifier  206  and the LED flash driver  204  are on. In this configuration, both the is_audio_on signal  214  and the is_flash_on signal  211  indicate to the controller  208  that LED flash driver  204  and audio amplifier  206  are on. The second exemplary IC operation configuration focuses on the LED flash driver  204  being on, but the LED flash driver  204  may be operating in a certain LED flash driver mode (e.g., movie mode or camera mode). 
     However, a problem may arise in this second exemplary IC operation configuration in that depending upon the power being dissipated by the audio amplifier  206 , the total power provided by the boost converter  202  to the LED flash driver  204  and audio class D amplifier  206  may not be enough to drive the LED flash driver  204  when the flash turns on. An example is shown in  FIG. 6  wherein the IC  200  is operating in the movie mode (e.g., a low power mode), such as when recording a movie, and wherein the amount of power required to record the movie (e.g., when the audio amplifier  206  is on and when the flash is either off or being operated at a low power mode) can be below the power threshold limit and therefore no attenuation of the audio amplifier  206  (such as, for example, the attenuation of the power or output signal of the audio amplifier  206 ) is required. However, as contrastingly shown in  FIG. 7 , when the IC  200  is in a camera mode (e.g., when flash is on and when LED flash is operated at a high or higher power mode), for example when taking a still photograph, a greater amount of power is required to drive the flash when the flash turns on and the total power required to drive the flash and the audio amplifier  206  may be greater than the power threshold limit. Therefore, there are two ways of handling and solving the situation of not having sufficient power supplied to both the LED flash driver  204  and audio class D amplifier  206  when both are on. 
     One exemplary way of solving the insufficient power problem to both the LED flash driver  204  and the class D audio amplifier  206  is to map the power supplied to the LED flash driver  204  and audio amplifier  206 . Mapping of the power by limiting the power to the audio amplifier  206  accordingly and only when necessary ensures that enough constant current is provided to the LED flash driver  204 .  FIG. 8  shows an exemplary power mapping chart that an algorithm which the controller  208  would incorporate to calculate and determine the amount of constant current required to be provided to the LED flash driver  204 . The first column shows the mode of operation that the IC  200  operates (e.g., the IC  200  mode of operation), such as the LED flash mode or audio amplifier mode. The second column shows the LED flash driver mode when the flash is on, such as the camera mode or the movie mode. The third column shows the amount of power P_boost provided by the boost converter  202 , and the fourth column shows the power required to drive the LED flash driver  204  (e.g., power P_Camera for camera mode, power P_Movie for movie mode, and 0 power for audio amplifier mode). The fifth right most column shows the equations used to calculate the amount of power provided to the audio amplifier  208 , which is the difference between the power P_boost provided by the boost converter  202  and the power required by the LED flash driver  204 . By mapping the power in this way between the two devices, boost converter  202  provides sufficient power and respective constant current for ensuring the driving of the LED flash driver  204 , and uses the remaining power for driving the audio amplifier  206 . 
       FIG. 9  shows an exemplary timing diagram of when the flash is turned on at higher audio signals. Exemplary timing diagram  1002  shows when the is_flash_on signal goes high at time T_flash. Exemplary timing diagram  1004  shows the boost voltage V_boost that is the output voltage of the boost converter  202  slightly decreasing at time T_flash. Timing diagram  1006  shows an exemplary audio output signal of audio amplifier  206 . In timing diagram  1006 , the audio output signal  1001  is shown as a small audio signal having a magnitude  1009  that stays within a power amplitude limit  1007 . Thus, in this case, no attenuation of the audio output signal  1001  is required. However, in timing diagram  1008 , the audio output signal  1001  is shown as a large audio signal having a magnitude  1011  before time T_flash that now extends beyond the power amplitude limit  1007 . In this latter case, attenuation of the audio output signal  1001  is required so that the audio amplifier  206  operates at a lower power having a magnitude  1009  that is within the power amplitude limit  1007 , as shown after time T_flash in  FIG. 9 . 
     A power limiting function power_limiter (see power_limiter in states  604  and  608  of state diagram  600  in  FIG. 10 ) is programmed in the controller  208 , and the power_limiter function is able to monitor overall total power through LED flash driver  204  and audio amplifier  206  and attenuate the magnitude of the power through the audio amplifier  206  if the magnitude is greater than the power amplitude limit, such as in accordance with the timing diagrams in  FIG. 9 . Therefore, the power_limiter function will attenuate the power to ensure the amount of power is within the power amplitude limit and map the power between the LED flash driver  204  and audio amplifier  206  accordingly. 
       FIG. 10  shows the state diagram  600  of an exemplary algorithm for controller  208 . State diagram  600  starts at the normal state  602 . At normal state  602 , the audio amplifier  206  is on and the LED flash driver  204  is off. The controller  208  waits to receive an indication of whether the LED flash driver mode is to be in the camera mode or movie mode. If controller  208  receives an is_camera_on signal that IC  200  is to operate in the camera mode, then the controller algorithm moves from normal state  602  to state  604  where the power_limiter function sets the power amplitude limit  1007  at a certain level to operate IC  200  in camera mode. Controller algorithm then moves from state  604  to state  605  where the IC  200  waits for the power_limiter function to act and adjust and output the power accordingly. Then the controller algorithm moves from state  605  to state  606  where IC  200  operates in the camera mode until the controller algorithm receives a camera_off signal indicating that IC  200  is no longer operating in the camera mode and returns back to normal state  602 . At normal state  602 , if controller  208  receives an is_movie_on signal  212  that indicates movie mode is to be turned on, the controller algorithm moves from normal state  602  to state  608 . At state  608 , the power_limiter function sets the power amplitude limit  1007  at a certain level to operate IC  200  in movie mode. From state  608 , the algorithm moves to state  609  where the IC  200  waits for the power_limiter to act and adjust and output the power respectively. Then the controller algorithm moves from state  609  to state  610  where IC  200  operates in the movie mode. From state  610 , if the controller algorithm receives a movie_off signal, then IC  200  is no longer operating in the movie mode and returns back to normal state  602 . Alternatively, at state  610 , if the controller algorithm receives an is_camera_on signal, then IC  200  moves from operating from the movie mode to the camera mode and controller algorithm moves from state  610  to state  604  and continues to operate therefrom. 
     Another exemplary method for solving the problem of when both the LED flash driver  204  and the class D audio amplifier  206  are on is to enable an audio volume control and allow the lowering of the volume output of audio amplifier  206  when necessary. In the case just where the class D audio amplifier  206  is on, the volume output signal may be set at an exemplary volume level of 18 dB. In the case of when both the LED driver  204  and audio amplifier  206  are on, the volume output signal of audio amplifier  206  is lowered in order to provide sufficient constant current to run through the LED flash driver  204 . Depending on whether the LED flash driver mode of operation is in camera or movie mode, the controller  208  lowers the volume accordingly. For example, in the movie mode, controller  208  decreases the volume output signal level to 15 dB, and in the camera mode, controller  208  decreases the volume output signal level to 12 dB. The lowering of the volume level accordingly allows for sufficient power to be supplied to the LED flash driver  204  and the audio amplifier  206 . 
     There are many benefits of the single integrated circuit for an audio subsystem with a boosted Class-D amplifier and integrated LED flash driver. Using a single boost converter to supply power to both the Class-D amplifier and the LED flash driver within a single integrated circuit allows for greater deliverance of power to the class D amplifier without any extra cost. Also with such integration into a single integrated circuit, there is an increase of efficiency because of the ability to limit and balance power of the total system. In addition, it allows for more flexible control to maximize the audio quality without sacrificing the chip area to handle the thermal stress from the LED driver. 
     Although embodiments have been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims.