High-resolution dimming circuit

Abstract

A dimming circuit for dimming according to a dimming code, comprising a light-emitting module, a first current source, a digital-to-analog converter, a switch, a second current source, and a pulse-width modulation generator. The light-emitting module is used to emit light according to a driving current. The first current source includes a first terminal coupled to a second terminal of the light-emitting module. The digital-to-analog converter is used to generate a DC voltage according to a DC dimming code signal to control the first current source. The switch includes a first terminal coupled to the second terminal of the light-emitting module. The second current source includes a first terminal coupled to a second terminal of the switch. The pulse-width modulation generator is used to generate a pulse-width modulation voltage according to a pulse-width modulation dimming code signal to control the second current source. The DC dimming code signal includes the most significant bit of the dimming code, and the pulse-width modulation dimming code signal includes the least significant bit of the dimming code.

Description

Technical Field

[0001] The present invention relates to a dimming circuit, and more particularly to a dimming circuit capable of separately processing high-resolution dimming codes. Background Art

[0002] Various displays, such as liquid crystal displays (LCDs), organic light emitting diode (OLED) displays, etc., can be applied to different electronic devices, such as consumer electronics products like televisions, computers, and handheld devices. Liquid crystal displays usually include a backlight to provide illumination to the liquid crystal layer, and a circuit controls the brightness and color of the pixels in the display to present the desired image.

[0003] Light emitting diodes (LEDs) are widely used in displays due to their many advantages such as small size, low power consumption, high luminous efficiency, and long lifespan. LED dimming technologies are mainly divided into analog dimming and pulse-width modulation dimming (PWM dimming).

[0004] Pulse-width modulation dimming technology achieves the purpose of dimming by changing the duty cycle. For example, 50% brightness can be achieved by applying 100% drive current at a 50% duty cycle. Therefore, the screen is not actually always on, but rather flickers at a high frequency between the fully on and fully off states. Due to the persistence of vision of the human eye, the screen appears to be always on. Pulse-width modulation dimming achieves the purpose of adjusting the screen brightness by controlling the frequency of the appearance of the on and off states. If the on time is long and the off time is short within the same cycle, the overall screen will be brighter, and vice versa. If the screen flickers below a certain frequency, the human eye is prone to discomfort, and long-term use may cause eye discomfort and even other adverse health conditions. At high frequencies, that is, when the screen brightness is relatively high, it generally does not cause discomfort, but when the screen brightness is low, the discomfort of the human eye is more obvious. Analog dimming changes the brightness of the screen by increasing or decreasing the power of the LED drive circuit, and the screen brightness can be changed simply by changing the voltage or current. For example, applying 50% drive current can achieve 50% brightness. The advantage of analog dimming is that it places less burden on the eyes when looking at the screen for a long time, while the disadvantage is that the uniformity and brightness accuracy of the screen display are not as good as those of pulse-width modulation dimming. Summary of the Invention

[0005] An embodiment provides a dimming circuit for dimming according to a dimming code, including a light-emitting module, a first current source, a digital-to-analog converter, a switch, a second current source, and a pulse-width modulation generator. The light-emitting module is configured to emit light according to a driving current, and includes a first terminal and a second terminal, and the first terminal is configured to receive a supply voltage. The first current source includes a first terminal, a second terminal, and a control terminal, the first terminal is coupled to the second terminal of the light-emitting module, and the second terminal is coupled to a ground terminal. The digital-to-analog converter is coupled to the control terminal of the first current source, and is configured to generate a DC voltage according to a DC dimming code signal to control the first current source. The switch includes a first terminal, a second terminal, and a control terminal, and the first terminal is coupled to the second terminal of the light-emitting module. The second current source includes a first terminal and a second terminal, the first terminal is coupled to the second terminal of the switch, and the second terminal is coupled to a ground terminal. The pulse-width modulation generator is coupled to the control terminal of the switch, and is configured to generate a pulse-width modulation voltage according to a pulse-width modulation dimming code signal to control the second current source. The DC dimming code signal includes the most significant bit of the dimming code, and the pulse-width modulation dimming code signal includes the least significant bit of the dimming code.

[0006] Another embodiment provides a dimming circuit for dimming according to a dimming code, including a light-emitting module, a first current source, a digital-to-analog converter, a switch, a second current source, and a pulse-width modulation generator. The light-emitting module is configured to emit light according to a driving current, and includes a first terminal and a second terminal, and the first terminal is configured to receive a supply voltage. The first current source includes a first terminal, a second terminal, and a control terminal, the first terminal is coupled to the second terminal of the light-emitting module, and the second terminal is coupled to a ground terminal. The digital-to-analog converter is coupled to the control terminal of the first current source, and is configured to generate a DC voltage according to a DC dimming code signal to control the first current source. The switch includes a first terminal, a second terminal, and a control terminal, and the first terminal is coupled to the second terminal of the light-emitting module. The second current source includes a first terminal and a second terminal, the first terminal is coupled to the second terminal of the switch, and the second terminal is coupled to a ground terminal. The pulse-width modulation generator is coupled to the control terminal of the switch, and is configured to generate a pulse-width modulation voltage according to a pulse-width modulation dimming code signal to control the second current source. The DC dimming code signal includes the most significant bit of the dimming code, and the pulse-width modulation dimming code signal includes the least significant bit of the dimming code. The light-emitting module includes a light-emitting diode and a margin control transistor.

[0007] An embodiment provides another dimming circuit for dimming according to a dimming code, including a light-emitting module, a first current source, a digital-to-analog converter, a switch, a second current source, and a controller. The light-emitting module is used to emit light according to a driving current, including a first end and a second end, and the first end is used to receive a supply voltage. The first current source includes a first end, a second end, and a control end, the first end is coupled to the second end of the light-emitting module, and the second end is coupled to the ground end. The digital-to-analog converter is coupled to the control end of the first current source and is used to generate a DC voltage according to a DC dimming code signal to control the first current source. The second current source includes a first end and a second end, the first end is coupled to the second end of the light-emitting module, and the second end is coupled to the ground end. The controller is coupled to the control end of the second current source and is used to generate a control voltage according to a pulse-width modulation dimming code signal to control the second current source. The DC dimming code signal includes the most significant bit of the dimming code, and the pulse-width modulation dimming code signal includes the least significant bit of the dimming code. Description of the Drawings

[0008] Figure 1 It is a schematic diagram of the dimming circuit according to the embodiment of the present invention.

[0009] Figures 2A - 2B For Figure 1 It is a schematic diagram of the dimming code and the corresponding driving current of the dimming circuit.

[0010] Figure 3 For Figure 1 It is a waveform schematic diagram of the DC current and the pulse-width modulation current of the dimming circuit.

[0011] Figure 4 It is a schematic diagram of the dimming circuit according to another embodiment of the present invention.

[0012] Figure 5 It is a schematic diagram of the dimming circuit according to another embodiment of the present invention.

[0013] Figure 6 For Figure 5 It is a schematic diagram of the pulse-width modulation voltage of the dimming circuit.

[0014] Figure 7 It is a schematic diagram of the dimming circuit according to another embodiment of the present invention.

[0015] Symbol Description

[0016] 100, 200, 400, 500: Dimming circuit

[0017] 110, 210, 410, 510: Light-emitting module

[0018] 120, 220, 420, 520: Digital-to-analog converter

[0019] 130, 230, 430: Pulse-width modulation generator

[0020] 530: Controller

[0021] LED: Light Emitting Diode

[0022] Vs: Supply Voltage

[0023] I LED : Drive Current

[0024] I DC : Direct Current

[0025] I PWM : Pulse Width Modulation Current

[0026] V DC : Direct Current Voltage

[0027] V PWM : Pulse Width Modulation Voltage

[0028] Vc: Control Voltage

[0029] DCcode: Direct Current Dimming Code Signal

[0030] PWMcode: Pulse Width Modulation Dimming Code Signal

[0031] T1: Switch

[0032] CS1, CS2: Current Source

[0033] GND: Ground Terminal

[0034] T2: Margin Control Transistor

[0035] Vhrc: Margin Control Voltage Detailed Implementation Manner

[0036] The illustrated architecture, number of components, number of layers, position distribution, ratio, etc. are only for examples to assist in explaining and understanding the embodiments, rather than to limit the forms and scopes of the embodiments. If ordinal numbers such as first and second are mentioned in this article, they are only used to distinguish different components, rather than to limit the sequence or importance.

[0037] Certain words will be used in this specification and claims to refer to specific components. Those skilled in the art should understand that technical documents may refer to the same component by different names. This article has no intention of distinguishing components with the same function but different names. In the specification and claims, words such as "having" and "including" are open-ended words, and thus should be interpreted as meaning "including but not limited to...".

[0038] Figure 1Schematic diagram of the dimming circuit 100 according to an embodiment of the present invention. The dimming circuit 100 is used to dim according to a dimming code. The dimming circuit 100 includes a light-emitting module 110, a first current source CS1, a digital-to-analog converter 120, a switch T1, a second current source CS2, and a pulse-width modulation generator (PWM generator) 130. The light-emitting module 110 is used to emit light according to a driving current I LED and includes a first end and a second end. The first end is used to receive a supply voltage Vs. The first current source CS1 includes a first end, a second end, and a control end. The first end is coupled to the second end of the light-emitting module 110, and the second end is coupled to a ground terminal GND. The digital-to-analog converter 120 is coupled to the control end of the first current source CS1 and is used to generate a DC voltage V DC to control the first current source CS1. The switch T1 includes a first end, a second end, and a control end. The first end is coupled to the second end of the light-emitting module 110. The switch T1 can be an N-type transistor or other equivalent components. The second current source CS2 includes a first end and a second end. The first end is coupled to the second end of the switch T1, and the second end is coupled to the ground terminal GND. The pulse-width modulation generator 130 is coupled to the control end of the switch T1 and is used to generate a pulse-width modulation voltage V PWM to control the switch T1. The DC dimming code signal DCcode includes the higher bits of the dimming code, which includes the most significant bit (MSB) of the dimming code. The pulse-width modulation dimming code signal PWMcode includes the lower bits of the dimming code, which includes the least significant bit (LSB) of the dimming code. In an application, the light-emitting module 110 can include a light-emitting diode LED. The first end of the light-emitting diode LED can receive the supply voltage Vs, and the second end can be coupled to the first end of the first current source CS1.

[0039] The driving current I LED for driving the light-emitting diode LED is controlled by the first current source CS1 and the second current source CS2. The DC current I DC and the pulse-width modulation current I PWM are added together to obtain the driving current I LED , and the brightness of the light-emitting diode LED is determined by the driving current I LED . The first current source CS1 is directly controlled by the DC voltage V DC to provide the DC current I DC . When the DC voltage V DC is higher, the DC current I DC is larger, and the brightness of the light-emitting diode LED is higher. The pulse-width modulation voltage V PWMThe controllable switch T1 is used to control the second current source CS2 and provide a pulse-width modulated current I PWM . Specifically, when the pulse-width modulated voltage V PWM is at a high level, the switch T1 conducts to generate a pulse-width modulated current I PWM ; when the pulse-width modulated voltage V PWM is at a low level, the switch T1 turns off to cut off the pulse-width modulated current I PWM . The higher the duty cycle of the pulse-width modulated voltage V PWM , the longer the time to generate the pulse-width modulated current I PWM , and the higher the brightness of the light-emitting diode LED. The control method of the driving current I LED generated by the dimming circuit 100 according to the dimming code will be described in detail below.

[0040] Figures 2A - 2B is Figure 1 a schematic diagram of the dimming code and the corresponding driving current I LED of the dimming circuit 100. Figure 2A The dimming code shown is 16 bits, including 12-bit DC code and 4-bit PWM code. The DC code includes the higher 12 bits of the dimming code, which includes the most significant bit of the dimming code, and the PWM code includes the lower 4 bits of the dimming code, which includes the least significant bit of the dimming code. Figure 2B The vertical axis shown is the driving current I LED , and the horizontal axis is the period, divided into 16 time slots. When inputting to the dimming circuit 100, the DC code and the PWM code can be processed separately. For example, the dimming code 32 (binary: 0000000000100000) can be converted to a DC code equal to 2, and a DC current I DC of 2 mA can be generated in the dimming circuit 100 and last for 16 time slots; the PWM code is equal to 0, so no pulse-width modulated current I PWM is generated. The dimming code 31 (binary: 0000000000011111) can be converted to a DC code equal to 1 and a PWM code equal to 15. A DC current I DC of 1 mA can be generated in the dimming circuit 100 and last for 16 time slots, and a pulse-width modulated current I PWM of 1 mA lasts for 15 time slots. The dimming code 18 (binary: 0000000000010010) can be converted to a DC code equal to 1 and a PWM code equal to 2. A DC current I DC of 1 mA can be generated in the dimming circuit 100 and last for 16 time slots, and a pulse-width modulated current I PWM of 1 mA lasts for 2 time slots; the dimming code 17 (binary: 0000000000010001) can be converted to a DC code equal to 1 and a PWM code equal to 1. A DC current I DCLasts for 16 time slots, and a pulse-width modulation current I of 1 mA PWM Lasts for 1 time slot, and so on. The DC current I DC And the pulse-width modulation current I PWM The sum of the currents is the drive current I LED . In this way, the brightness generated by dimming code 32 is higher than that of dimming code 31, and the brightness generated by dimming code 18 is higher than that of dimming code 17.

[0041] As described above, the DC code can be converted into a DC dimming code signal DCcode and input into the digital-to-analog converter 120. The digital-to-analog converter 120 then converts the DC dimming code signal DCcode into a DC voltage V DC , controlling the first current source CS1 to provide a DC current I DC . The PWM code can be converted into a pulse-width modulation dimming code signal PWMcode and input into the pulse-width modulation generator 130. The pulse-width modulation generator 130 then converts the pulse-width modulation dimming code signal PWMcode into a pulse-width modulation voltage V PWM . The pulse-width modulation voltage V PWM Then rapidly switches the switch T1, enabling the second current source CS2 to provide a pulse-width modulation current I with a pulse-width modulation waveform PWM .

[0042] Figure 3 Is Figure 1 A waveform diagram of the DC current IDC and the pulse-width modulation current IPWM of the dimming circuit 100. The DC current I DC The waveform formula is as follows:

[0043]

[0044] DC Hightime = 100% Period

[0045] Amplitude is the amplitude, I LEDMAX Is the maximum drive current of the light-emitting diode LED. DC_code is the DC code. DC_resolution is the DC code bit. For example, in this embodiment, the DC code is 12 bits. Hightime is the high-level duration, that is, 100% of the period (Period).

[0046] The waveform formula of the pulse-width modulation current IPWM is as follows:

[0047]

[0048]

[0049] Amplitude is the amplitude, I LEDMAXis the maximum drive current of the light-emitting diode LED. DC_code is the DC code. PWM_code is the PWM code. DC_resolution is the DC code bit. For example, in this embodiment, the DC code is 12 bits. Hightime is the high-level duration. DC_resolution is the DC code bit. For example, in this embodiment, the DC code is 12 bits. PWM_resolution is the PWM code bit. For example, in this embodiment, the PWM code is 4 bits. Period is the period time. By using the above formula, the waveform such as Figure 3 can be obtained.

[0050] The 16-bit dimming code currently belongs to a relatively high resolution in the dimming field, that is, a relatively large number of bits. If the 16-bit dimming code completely uses analog dimming to adjust the brightness of the light-emitting diode LED, there is likely to be a situation of uneven color. Moreover, the 16-bit digital-to-analog converter circuit structure requires more transistors, and the occupied circuit area is too large to be effectively integrated into a small-size chip. In addition, if the 16-bit dimming code completely uses pulse-width modulation dimming to adjust the brightness of the light-emitting diode LED, it cannot effectively provide a linear brightness perception for the human eye. Because although the duty cycle of the drive current of the light-emitting diode LED can change linearly, the human eye's visual perception range is not a linear change of relative brightness, but a logarithmic change. Therefore, integrating analog dimming and pulse-width modulation dimming in the embodiment can make up for each other's deficiencies to achieve the best brightness presentation method. The present invention includes but is not limited to 16 bits, and other numbers of bits should also fall within the scope of the present invention.

[0051] Figure 4 is a schematic diagram of the dimming circuit 200 according to an embodiment of the present invention. The dimming circuit 200 is used to dim according to the dimming code. The dimming circuit 200 includes a light-emitting module 210, a first current source CS1, a digital-to-analog converter 220, a switch T1, a second current source CS2, and a pulse-width modulation generator 230. The light-emitting module 210 is used to emit light according to the drive current I LED and includes a first end and a second end. The first end is used to receive the supply voltage Vs. The first current source CS1 includes a first end, a second end, and a control end. The first end is coupled to the second end of the light-emitting module 210, and the second end is coupled to the ground terminal GND. The digital-to-analog converter 220 is coupled to the control end of the first current source CS1 and is used to generate a DC voltage V according to the DC dimming code signal DCcode DCto control the first current source CS1. The switch T1 includes a first terminal, a second terminal, and a control terminal. The first terminal is coupled to the second terminal of the light-emitting module 210. The switch T1 can be an N-type transistor or other equivalent components. The second current source CS2 includes a first terminal and a second terminal. The first terminal is coupled to the second terminal of the switch T1, and the second terminal is coupled to the ground terminal GND. The pulse-width modulation generator 230 is coupled to the control terminal of the switch to generate a pulse-width modulation voltage V according to the pulse-width modulation dimming code signal PWMcode PWM to control the switch T1. The DC dimming code signal DCcode includes the higher bits of the dimming code, which includes the most significant bit (MSB) of the dimming code. The pulse-width modulation dimming code signal PWMcode includes the lower bits of the dimming code, which includes the least significant bit (LSB) of the dimming code. The driving current I for driving the light-emitting diode LED LED is controlled by the first current source CS1 and the second current source CS2. The DC current I DC and the pulse-width modulation current I PWM The sum of the currents is the driving current I LED and the brightness of the light-emitting diode LED is determined by the driving current I LED determined.

[0052] The difference between the dimming circuit 200 and the dimming circuit 100 is that the dimming circuit 200 has a headroom control mechanism. The light-emitting module 210 can include a light-emitting diode LED and a headroom control transistor T2. The first terminal of the light-emitting diode LED can receive the supply voltage Vs. The first terminal of the headroom control transistor T2 is coupled to the second terminal of the light-emitting diode LED, the second terminal is coupled to the first terminal of the first current source CS1, and the control terminal is used to receive the headroom control voltage Vhrc. The headroom control mechanism is used to approximately control the voltage of the light-emitting module 210 at a fixed value or less than a threshold value to reduce power consumption. The headroom control voltage Vhrc needs to be dynamically adjusted according to the voltage at the second terminal of the light-emitting module 210 to control the forward voltage shift of the light-emitting diode LED. In other words, the headroom control voltage Vhrc is a feedback mechanism. When the pulse-width modulation voltage VPWM changes greatly and the voltage of the light-emitting module 210 jitters greatly, the dimming circuit 200 can adjust the headroom control voltage Vhrc to keep the voltage of the light-emitting module 210 approximately at a fixed value. In other words, the headroom control transistor T2 can be regarded as a variable resistor of a low-dropout regulator. The resistance value is adjusted by the headroom control voltage Vhrc to reduce the power consumption of the dimming circuit 200 and extend the service life of the light-emitting diode LED.

[0053] Figure 5Schematic diagram of the dimming circuit 400 according to an embodiment of the present invention. The dimming circuit 400 is used to perform dimming according to a dimming code. The dimming circuit 400 includes a light-emitting module 410, a first current source CS1, a digital-to-analog converter 420, a switch T1, a second current source CS2, and a pulse-width modulation generator (PWM generator) 430. The light-emitting module 110 is used to emit light according to the driving current I LED and includes a first end and a second end. The first end is used to receive the supply voltage Vs. The first current source CS1 includes a first end, a second end, and a control end. The first end is coupled to the second end of the light-emitting module 410, and the second end is coupled to the ground terminal GND. The digital-to-analog converter 420 is coupled to the control end of the first current source CS1 and is used to generate a DC voltage V DC to control the first current source CS1. The switch T1 includes a first end, a second end, and a control end. The first end is coupled to the second end of the light-emitting module 410. The switch T1 can be an N-type transistor or other equivalent components. The second current source CS2 includes a first end and a second end. The first end is coupled to the second end of the switch T1, and the second end is coupled to the ground terminal GND. The pulse-width modulation generator 430 is coupled to the control end of the switch and is used to generate a pulse-width modulation voltage V PWM to control the switch T1. The DC dimming code signal DCcode includes the higher bits of the dimming code, which includes the most significant bit (MSB) of the dimming code. The pulse-width modulation dimming code signal PWMcode includes the lower bits of the dimming code, which includes the least significant bit (LSB) of the dimming code. In application, the light-emitting module can include a light-emitting diode LED. The first end of the light-emitting diode LED can receive the supply voltage Vs, and the second end can be coupled to the first end of the first current source CS1. The driving current I LED for driving the light-emitting diode LED is controlled by the first current source CS1 and the second current source CS2. The DC current I DC and the pulse-width modulation current I PWM are added together to form the driving current I LED , and the brightness of the light-emitting diode LED is determined by the driving current I LED .

[0054] The difference between the dimming circuit 400 and the dimming circuit 100 is that the pulse width modulation generator 430 may include a digital circuit 440, such as a Lookup Table, and is implemented in hardware, such as a Read-Only Memory (ROM), an Application Specific Integrated Circuit (ASIC), or other forms of digital circuits. The digital circuit 440 can be used to generate Dithering. By adding dithering, for example, Spread Spectrum Clock Generation, quantization error and audio interference (noise) in the audible frequency range of the human ear can be reduced in the low bit part, thereby enabling the dimming circuit 400 to provide more accurate brightness. The digital circuit 440 can also be applied in the same way, such as Spread Spectrum Clock Generation, to reduce the Electromagnetic Interference (EMI) generated by the pulse width modulation voltage V PWM By adding dithering, for example, Spread Spectrum Clock Generation, quantization error and audio interference (noise) in the audible frequency range of the human ear can be reduced in the low bit part, thereby enabling the dimming circuit 400 to provide more accurate brightness. The digital circuit 440 can also be applied in the same way, such as Spread Spectrum Clock Generation, to reduce the Electromagnetic Interference (EMI) generated by the pulse width modulation voltage V PWM in the high bit part.

[0055] The digital circuit 440 can also be used to cause the pulse width modulation voltage V PWM to generate a Phase-shift, so that the start times of the pulse width modulation voltages V PWM of multiple dimming circuits 400 can be staggered. For example, a 16-channel driving device has multiple dimming circuits 400 integrated into an integrated circuit. If all the pulse width modulation voltages V PWM rise or fall at the same time, it will cause a sharp voltage drawdown, causing the circuit to exceed the load. Adding a Phase-shift to the pulse width modulation voltage V PWM can avoid the above situation and enable the dimming circuit 400 to operate stably.

[0056] Figure 6 is a schematic diagram of the pulse width modulation voltage V PWM of the dimming circuit 400. Figure 6 The upper half is the pulse width modulation voltage V PWM without added dithering, and the lower half is the pulse width modulation voltage V PWM with added dithering. For example, the digital circuit 440 can apply Spread Spectrum Clock Generation to disperse the spectrum of the pulse width modulation voltage V PWM . As shown in Figure 6 the lower half, the pulse width modulation voltage V PWMAs shown, the waveforms in both period N and period N+1 are of the 3+2 type, which can reduce quantization error and audio interference to the human ear. Moreover, the digital circuit 440 can also output other special waveforms based on the same principle to reduce the high-frequency electromagnetic interference (EMI) of the dimming circuit 400. Therefore, adding dithering using the digital circuit 440 can make the driving current I LED more stable, reduce the flicker of the light-emitting diodes, and make the brightness more accurate.

[0057] Here, it should be added that the spread spectrum clock generation technology is an application of frequency modulation. The most basic principle of the spread spectrum clock is to slightly modulate the frequency of the clock, so that the energy of the signal is dispersed within a controllable small range. After spread spectrum modulation, the peak energy of each harmonic on the spectrum will disappear. The higher the harmonic term, the greater the spread spectrum amount generated, and therefore, the more obvious the attenuation of the peak energy. What is restricted by electromagnetic interference or audio interference is the peak emission at a specific frequency, rather than the average peak emission of the entire spectrum. Therefore, using the spread spectrum clock can effectively reduce the electromagnetic interference or audio interference of the signal.

[0058] Figure 7 is a schematic diagram of the dimming circuit 500 according to an embodiment of the present invention. The dimming circuit 500 is used to dim according to the dimming code, and includes a light-emitting module 510, a first current source CS1, a digital-to-analog converter 520, a switch T1, a second current source CS2, and a controller 530. The light-emitting module is used to emit light according to the driving current I LED and includes a first end and a second end. The first end is used to receive the supply voltage Vs. The first current source CS1 includes a first end, a second end, and a control end. The first end is coupled to the second end of the light-emitting module 510, and the second end is coupled to the ground terminal GND. The digital-to-analog converter 520 is coupled to the control end of the first current source CS1 and is used to generate a DC voltage V DCto control the first current source CS1. The second current source CS2 includes a first end and a second end. The first end is coupled to the second end of the light-emitting module 510, and the second end is coupled to the ground terminal GND. The controller 530 is coupled to the control terminal of the second current source to generate a control voltage Vc according to the pulse-width modulation dimming code signal PWMcode to control the second current source CS2. The DC dimming code signal DCcode includes the higher bits of the dimming code, which includes the most significant bit (MSB) of the dimming code. The pulse-width modulation dimming code signal PWMcode includes the lower bits of the dimming code, which includes the least significant bit (LSB) of the dimming code. The driving current I for driving the light-emitting diode LED LED is controlled by the first current source CS1 and the second current source CS2. The DC current I DC and the pulse-width modulation current I PWM The total current of the sum is the driving current I LED and the brightness of the light-emitting diode LED is determined by the driving current I LED .

[0059] The difference between the dimming circuit 500 and the dimming circuit 100 is that the second current source CS2 is an adjustable current source, and its output current is controlled by the controller 530. Therefore, the switch T1 of the dimming circuit 100 can be omitted in the dimming circuit 500. The controller 530 can be specifically implemented by a digital circuit, such as a lookup table (Lookup Table) or other equivalent circuit architectures, which can convert the pulse-width modulation dimming code signal PWMcode into a control voltage Vc. In addition, the controller 530 can also cause the control voltage Vc to generate a phase shift, so that the start times of the control voltages Vc of multiple dimming circuits 500 can be staggered. For example, in a 16-channel driving device, multiple dimming circuits 500 are integrated into an integrated circuit. If all the pulse-width modulation voltages V PWM rise or fall at the same time, it will cause a sharp voltage drawdown, causing the circuit to exceed the load. Adding a phase shift to the control voltage Vc can avoid the above situation and make the dimming circuit 500 operate stably.

[0060] Furthermore, the controller 530 can generate control voltages Vc with different amplitudes, control the second current source CS2 to output pulse-width modulation currents I with different amplitudes and different pulse widths PWM, to produce a dithering effect. By adding dithering to the control voltage Vc, quantization error and audio interference at audible frequencies for the human ear can be reduced, thereby enabling the dimming circuit 500 to provide more accurate brightness. The controller 530 can also apply the same method to reduce the electromagnetic interference (EMI) of the control voltage Vc, making the driving current I LED more stable to reduce the flicker of the light-emitting diode LED.

[0061] In summary, the dimming circuits of the above embodiments of the present invention can divide a high-resolution dimming code into a DC code and a PWM code, which respectively contain the higher bits and the lower bits of the dimming code. Separately inputting the dimming code into the dimming circuit can reduce the control difficulty, lower the voltage level change to reduce perturbation and reduce the error rate. And the layout method of the dimming circuit can reduce the integrated circuit area. The dimming circuit of the embodiment can also apply a digital circuit to add dithering to suppress electromagnetic interference and audio interference, improving the brightness control accuracy.

[0062] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. A dimmer circuit, for dimming according to a dimming code, comprising: A light-emitting module, for emitting light according to a driving current, comprising: A first terminal, for receiving a supply voltage; and A second terminal; A first current source, comprising: A first terminal, coupled to the second terminal of the light-emitting module; A second terminal, coupled to a ground terminal; and A control terminal; A digital-to-analog converter, coupled to the control terminal of the first current source, for generating a DC voltage according to a DC dimming code signal to control the first current source; A switch, comprising: A first terminal, coupled to the second terminal of the light-emitting module; A second terminal; and A control terminal; A second current source, comprising: A first terminal, coupled to the second terminal of the switch; and A second terminal, coupled to the ground terminal; and A pulse-width modulation generator, coupled to the control terminal of the switch, for generating a pulse-width modulation voltage according to a pulse-width modulation dimming code signal to control the second current source; Wherein the DC dimming code signal comprises the most significant bit of the dimming code, and the pulse-width modulation dimming code signal comprises the least significant bit of the dimming code.

2. The dimmer circuit according to claim 1, wherein the light-emitting module comprises a light-emitting diode, comprising: A first terminal, for receiving the supply voltage; and A second terminal, coupled to the first terminal of the first current source.

3. The dimmer circuit according to claim 1, wherein the light-emitting module comprises: A light-emitting diode, comprising: A first terminal, for receiving the supply voltage; and A second terminal; and A margin control transistor, comprising: A first terminal, coupled to the second terminal of the light-emitting diode; A second terminal, coupled to the first terminal of the first current source; and A control terminal, for receiving a margin control voltage.

4. The dimmer circuit according to claim 1, wherein the pulse-width modulation generator comprises a look-up table for generating dithering and / or phase-shift for the pulse-width modulation voltage.

5. The dimmer circuit according to any one of claims 1 to 4, wherein the switch is an N-type transistor.

6. The dimmer circuit according to any one of claims 1 to 4, wherein the dimming code is 16 bits.

7. A dimmer circuit, for dimming according to a dimming code, comprising: A light-emitting module, for emitting light according to a driving current, comprising: A first terminal, for receiving a supply voltage; and A second terminal; A first current source, comprising: A first terminal, coupled to the second terminal of the light-emitting module; A second terminal, coupled to a ground terminal; and A control terminal; A digital to analog converter, coupled to the control terminal of the first current source, for generating a DC voltage according to a DC dimming code signal to control the first current source; A second current source, comprising: A first terminal, coupled to the second terminal of the light-emitting module; A second terminal, coupled to the ground terminal; and A control terminal; A controller, coupled to the control terminal of the second current source, is configured to generate a control voltage according to a pulse-width modulation dimming code signal to control the second current source to output a pulse-width modulation current with different amplitudes and different pulse widths; wherein the DC dimming code signal includes the most significant bit of the dimming code, and the pulse-width modulation dimming code signal includes the least significant bit of the dimming code.

8. The dimming circuit according to claim 7, wherein the light-emitting module includes a light-emitting diode, comprising: a first terminal for receiving the supply voltage; and a second terminal coupled to the first terminal of the first current source.

9. The dimming circuit according to claim 7, wherein the controller includes a look-up table for generating dithering and / or phase-shift for the control voltage.

10. The dimming circuit according to any one of claims 7 to 9, wherein the dimming code is 16 bits.

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