[0032] The preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described here are only used to illustrate and explain the present invention, and are not used to limit the present invention.
[0033] An embodiment of a DC-DC converter using digital PWM control
[0034] According to an embodiment of the present invention, a constant current type DC-DC converter adopting digital PWM control is provided. Such as figure 2 As shown, the power stage and the digital PWM control stage electrically connected in this embodiment, the constant current control stage electrically connected to the power stage and the digital PWM control stage, and the constant current control stage electrically connected between the power stage and the constant current control stage LED lights in series.
[0035] Among them, the above-mentioned digital PWM control stage includes a digital PWM modulator, an up/down counter, a first comparator, and an oscillator for generating a clock signal; the output terminal of the oscillator is respectively connected to the control terminal of the digital PWM modulator, And the control terminal of the up/down counter is connected; the non-inverting input terminal of the first comparator is electrically connected to the constant current control stage, the inverting input terminal is the first reference voltage V1 input terminal, and the output terminal is used to output logic level signals PG, It is electrically connected to the input end of the up/down counter; the output end of the up/down counter is electrically connected to the input end of the digital PWM modulator; and the output end of the digital PWM modulator is electrically connected to the power stage.
[0036] The above constant current control stage includes a power transistor M2, a second amplifier and a current setting resistor for setting the output current; The non-inverting input terminal of the second amplifier is the second reference voltage V2 input terminal, and the inverting input terminal is the voltage The input terminal is connected to the source of the power transistor M2, and the resistance is set by the current Connected to signal ground, the output terminal is connected to the gate of the power transistor M2; the drain of the power transistor M2 is voltage The output terminal is electrically connected with the in-phase input terminal of the first comparator, and is electrically connected with the series stage or power stage of the LED lamp.
[0037] The above LED lamp series stage includes a first light emitting diode D2 and a second light emitting diode D3 connected in series; the anode of the first light emitting diode D2 is electrically connected to the power stage, and the cathode is electrically connected to the anode of the second light emitting diode D3; and the second light emitting diode The cathode of D3 is electrically connected to the drain of the power transistor M2.
[0038] The above power stage includes an inductor L1, a diode D1, a power transistor M1, and a capacitor C1; the first connection terminal of the inductor L1 is connected to the DC input voltage , The second connection terminal is connected to the anode of the diode D1 and the drain of the power transistor M1, the gate of the power transistor M1 is connected to the output terminal of the digital PWM modulator, the source is connected to the signal ground, the drain is used as the switch control terminal SW, and the diode D1 The cathode of the capacitor C1 is grounded and used as the output voltage The output terminal of is electrically connected to the anode of the first light emitting diode D2.
[0039] The constant current DC-DC converter adopting digital PWM control of the above embodiment can be used to stabilize the output voltage of the DC-DC converter. The DC-DC converter adopting digital PWM control adopts the DC-DC controlled by digital PWM. The working principle of the converter is as follows:
[0040] See figure 2 , The second comparator compares the voltage of the cathode of the second light-emitting diode D3 Compared with the first reference voltage V1, the logic level signal PG is output; the up/down counter is an addition/subtraction counter, and it outputs an n-bit binary digital signal. When the logic level signal PG is a high level signal, it adds/subtracts The counter works in the state of the subtraction counter, and after each clock cycle, the output n-bit digital signal is reduced by 1; when the logic level signal PG is a low-level signal, the up/down counter works in the state of the addition counter, every time a clock is passed Cycle, the output n-bit digital signal plus 1. The digital PWM modulator generates a PWM duty cycle signal to drive the power transistor M1; the duty cycle output of the digital PWM modulator is determined by the size of the n-bit digital signal output by the up/down counter, and the n-bit digital signal increases by 1 every time , The duty cycle increases by a fixed time step DT; each time the n-bit digital signal decreases by 1, the duty cycle decreases by a fixed time step DT. By setting the number of bits and the time step DT of the digital signal, the maximum duty cycle that the digital PWM modulator can output can be set.
[0041] Using the constant current DC-DC converter adopting digital PWM control of the above embodiment, the principle of regulating the output voltage of the DC-DC converter is as follows:
[0042] When the output voltage of the DC-DC converter Too low, resulting in voltage When it is lower than the first reference voltage V1, the logic level signal PG output by the first comparator is a low level signal, the up/down counter works in the up counter state, and the output n-bit digital signal increases continuously, which makes the digital PWM modulation The duty cycle signal output by the converter is correspondingly increasing, resulting in the output of the DC-DC converter Increase
[0043] When the output voltage of the DC-DC converter Too high, resulting in voltage When it is higher than the reference voltage V1, the logic level signal PG output by the comparator is high and high, the up/down counter works in the state of the subtraction counter, and the output n-bit digital signal is continuously reduced, making the output of the digital PWM modulator account for The air ratio signal is correspondingly continuously reduced, resulting in the output of the DC-DC converter Reduce
[0044] Finally, the voltage Stabilized at a state close to the first reference voltage V1, and the output voltage of the DC-DC converter Stable on the adaptive voltage that automatically adapts to the number of LED lights (ie light-emitting diodes) in series in the LED light series stage, and the adaptive voltage is equal to the voltage Add the sum of the forward conduction voltages of all series-connected LED lamps (ie, light-emitting diodes) in the LED lamp series stage.
[0045] Examples of constant current LED driving DC-DC converter
[0046] According to an embodiment of the present invention, a constant current type LED driving DC-DC converter based on the above embodiment of a constant current type DC-DC converter adopting digital PWM control is provided. Such as image 3 As shown, this embodiment includes a DC-DC conversion stage and an LED lamp series stage electrically connected to the DC-DC conversion stage.
[0047] Among them, the above-mentioned DC-DC conversion stage includes an inductor L1, a diode D1, a high-power high-brightness boost LED driver chip A (Chip A) using digital PWM control, and a capacitor C1; the first connection terminal of the inductor L1 is connected to the DC input Voltage , The second connection terminal is connected to the anode of the diode D1 and the switch control terminal SW of the drive chip A; the cathode of the diode D1 is grounded through the capacitor C1 and is used as the output voltage The output terminal is electrically connected with the LED lamp in series; the drive chip A The terminal is electrically connected to the first connection terminal of the inductor L1, the DIM terminal is the dimming control port, and the GND terminal is connected to the signal ground. The terminal is electrically connected in series with the LED lamp.
[0048] The above LED lamp series stage includes a first light emitting diode D2 and a second light emitting diode D3 connected in series; the anode of the first light emitting diode D2 is electrically connected to the cathode of the diode D1, and the cathode is electrically connected to the anode of the second light emitting diode D3; The cathode of the light-emitting diode D3, and the driver chip A Terminals are electrically connected.
[0049] The constant current LED driving DC-DC converter of the above embodiment is based on the digital PWM control method of the above embodiment of the DC-DC converter using digital PWM control. The constant current effect is good, and the chip area is small, which can effectively reduce the cost. .
[0050] In summary, the constant current DC-DC converter and the constant current LED drive DC-DC converter using digital PWM control according to the embodiments of the present invention are based on the digital PWM control method. The circuit is very simple and the chip area is very small. Small, can effectively reduce costs; although the voltage The ripple voltage of the DC-DC converter is larger than that of the ordinary analog PWM control, but due to the constant current control part of the voltage The good suppression of the ripple voltage makes the ripple current of the LED lamp (ie, light-emitting diode) very small, and the constant current effect is very good.
[0051] Finally, it should be noted that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, it is still for those skilled in the art. The technical solutions described in the foregoing embodiments may be modified, or some of the technical features may be equivalently replaced. Any modification, equivalent replacement, improvement, etc., made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
