CN115037154A - Switching power supply system and control chip and control method thereof - Google Patents

Switching power supply system and control chip and control method thereof Download PDF

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Publication number
CN115037154A
CN115037154A CN202210567260.1A CN202210567260A CN115037154A CN 115037154 A CN115037154 A CN 115037154A CN 202210567260 A CN202210567260 A CN 202210567260A CN 115037154 A CN115037154 A CN 115037154A
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control signal
signal
generating
reference voltage
current
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朱力强
李萌
方烈义
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On Bright Electronics Shanghai Co Ltd
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On Bright Electronics Shanghai Co Ltd
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Priority to TW111137370A priority patent/TWI831398B/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1584—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A switching power supply system, a control chip and a control method thereof are provided. The switching power supply system comprises an inductor and a power switch, and the control chip is configured to: generating a turn-off control signal for controlling the power switch to change from an on state to an off state based on a dimming control signal for adjusting the brightness of the light emitting diode, a current detection signal for characterizing an inductor current flowing through the inductor, and a first reference voltage; generating an on control signal for controlling the power switch to change from an off state to an on state based on the dimming control signal, the current detection signal, a demagnetization detection signal for representing the demagnetization condition of the inductor, and a second reference voltage; and generating a pulse width modulation signal for controlling the on and off of the power switch based on the off control signal and the on control signal, wherein the first reference voltage is used for controlling the magnitude of the system output current of the switching power supply system, and the second reference voltage is used for controlling the duration of the power switch in the off state.

Description

Switching power supply system, control chip and control method thereof
Technical Field
The invention relates to the field of circuits, in particular to a switching power supply system, a control chip and a control method thereof.
Background
A switching power supply, also called a switching power supply or a switching converter, is a kind of power supply. The function of the switching power supply is to convert a voltage of one level into a voltage or a current required by a user terminal through various types of architectures (e.g., a flyback (flyback) architecture, a BUCK (BUCK) architecture, or a BOOST (BOOST) architecture).
Disclosure of Invention
According to the embodiment of the invention, the control chip for the switching power supply system comprises an inductor and a power switch, and is configured to: generating a turn-off control signal for controlling the power switch to change from an on-state to an off-state based on a dimming control signal for adjusting the brightness of the light emitting diode, a current detection signal for characterizing an inductor current flowing through an inductor, and a first reference voltage; generating an on control signal for controlling the power switch to change from an off state to an on state based on the dimming control signal, the current detection signal, a demagnetization detection signal for representing the demagnetization condition of the inductor, and a second reference voltage; and generating a pulse width modulation signal for controlling the on and off of the power switch based on the off control signal and the on control signal, wherein the first reference voltage is used for controlling the magnitude of the system output current of the switching power supply system, and the second reference voltage is used for controlling the duration of the power switch in the off state.
According to the embodiment of the invention, the control method for the switching power supply system comprises an inductor and a power switch, and comprises the following steps: generating a turn-off control signal for controlling the power switch to change from an on-state to an off-state based on a dimming control signal for adjusting the brightness of the light emitting diode, a current detection signal for characterizing an inductor current flowing through an inductor, and a first reference voltage; generating an on control signal for controlling the power switch to change from an off state to an on state based on the dimming control signal, the current detection signal, a demagnetization detection signal for representing the demagnetization condition of the inductor, and a second reference voltage; and generating a pulse width modulation signal for controlling the on and off of the power switch based on the off control signal and the on control signal, wherein the first reference voltage is used for controlling the magnitude of the system output current of the switching power supply system, and the second reference voltage is used for controlling the duration of the power switch in the off state.
The switching power supply system according to the embodiment of the invention comprises the control chip.
Drawings
The invention may be better understood from the following description of specific embodiments thereof taken in conjunction with the accompanying drawings, in which:
fig. 1 shows an example circuit diagram of a switching power supply system for dimmable LED lighting according to an embodiment of the invention.
FIG. 2 illustrates an example circuit diagram of the constant current control module shown in FIG. 1.
Fig. 3 shows an example circuit diagram of the compensation signal processing circuit shown in fig. 2.
Fig. 4 is a waveform diagram illustrating operations of a plurality of signals in the constant current control module shown in fig. 2.
Fig. 5 illustrates an example circuit diagram of the dimming signal processing unit illustrated in fig. 2.
Fig. 6 illustrates an example circuit diagram of the digital cell 216 shown in fig. 2.
Detailed Description
Features and exemplary embodiments of various aspects of the present invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is in no way limited to any specific configuration and algorithm set forth below, but rather covers any modification, replacement or improvement of elements, components or algorithms without departing from the spirit of the invention. In the drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessarily obscuring the present invention.
In recent years, Light Emitting Diodes (LEDs) have been widely used in various aspects of social production and life due to their long life, low cost, and small size compared to conventional incandescent, halogen, or fluorescent lighting products. The brightness of the LED is mainly controlled by the current flowing through the LED, and the brightness of the LED can be adjusted by adjusting the current flowing through the LED.
In a switching power supply system for LED lighting, adjusting the brightness of an LED by controlling the current flowing through the LED in a Pulse Width Modulation (PWM) chopping mode easily generates stroboscopic light. To prevent strobing, the brightness of the LED is typically adjusted by adjusting the current through the LED in a continuously varying analog manner. However, in the case of implementing LED low-brightness illumination, when the brightness of the LED is deeply adjusted in an analog manner, there are cases where a detected signal is weak and is not easily detected, and there is a problem that an input offset voltage of an internal circuit of a control chip in a switching power supply system for LED illumination causes insufficient adjustment depth for the brightness of the LED.
In view of the above problems, the switching power supply system, the control chip and the control method thereof according to the embodiments of the present invention are provided, which can realize the depth adjustment of the brightness of the LED in an analog manner.
Fig. 1 shows an example circuit diagram of a switching power supply system 100 for dimmable LED lighting according to an embodiment of the invention. As shown in fig. 1, the switching power supply system 100 adopts a BUCK architecture, and includes a rectifier BD1, an input capacitor C1, a diode D1, an inductor L1, an output load capacitor C2, a power switch Q1, a current detection resistor R1, and a control chip 102, wherein: the line voltage VIN supplies power to the control chip 102 via the HV pin of the control chip 102; the control chip 102 outputs a Gate driving signal Gate for driving the power switch Q1 to be turned on and off, based on a dimming control signal DIM for adjusting the brightness of the LED and a current detection signal CS representing an inductor current IL (not shown in the figure) flowing through an inductor L1.
As shown in fig. 1, the control chip 102 includes a low dropout regulator (LDO) module 1022, a demagnetization detection module 1024, a constant current control module 1026, and a driver module 1028, wherein: the low dropout regulator module 1022 supplies power to the internal circuit of the control chip 102 based on the line voltage VIN; the demagnetization detection module 1024 generates a demagnetization detection signal Dem indicating the demagnetization of the inductor L1 based on the Gate driving signal Gate and outputs the demagnetization detection signal Dem to the constant current control module 1026 (it should be understood that the manner in which the demagnetization detection module 1024 detects the demagnetization of the inductor L1 is not limited thereto, and the demagnetization detection module 1024 may generate the demagnetization detection signal Dem based on a demagnetization detection related signal received from the outside via a chip pin); the constant current control module 1026 generates a pulse width modulation signal PWM for controlling on and off of the power switch Q1 based on the reference voltage Vref, the demagnetization detection signal Dem, and the current detection signal CS, and outputs the pulse width modulation signal PWM to the driver module 1028; the driver module 1028 generates the Gate driving signal Gate based on the pulse width modulation signal PWM and outputs the Gate driving signal Gate to the Gate of the power switch Q1. Here, the dimming control signal DIM may be a direct current voltage signal or a pulse width modulation pulse signal, and is used for controlling the magnitude of the system output current Iout (i.e., the current flowing through the LED); a demagnetization detection signal Dem participates in constant current control and dimming control of the system; the current detection signal CS is used to implement closed-loop constant current control of the switching power supply system 100.
In the switching power supply system 100 shown in fig. 1, the system constant current control and the dimming control are mainly realized by the constant current control module 1026. Fig. 2 shows an example circuit diagram of the constant current control module 1026 shown in fig. 1. As shown in fig. 2, the constant current control module 1026 is configured to: generating an off control signal PWM _ off for controlling the power switch Q1 to change from the on state to the off state based on the dimming control signal DIM, the current detection signal CS, and the reference voltage Vref; generating an on control signal PWM _ on (not shown in the drawing) for controlling the power switch Q1 to change from an off state to an on state based on the dimming control signal DIM, the current detection signal CS, the demagnetization detection signal Dem, and the reference voltage V1; and generating a pulse width modulation signal PWM for controlling on and off of the power switch Q1 based on the off control signal PWM _ off and the on control signal PWM _ on, wherein the reference voltage Vref is used for controlling the magnitude of the system output current Iout of the switching power supply system 100, and the reference voltage V1 is used for controlling the duration of the off state of the power switch Q1.
As shown in fig. 2, in some embodiments, the constant current control module 1026 includes a dimming signal processing unit 202, a sampling unit 204, an error amplifier 206, a capacitor C201, a detection unit 208, a comparator 210, a clamping unit 212, a delay signal generation unit 214, and a digital unit 216, and the input signals of the constant current control module 1026 include a dimming control signal DIM, a current detection signal CS, a demagnetization detection signal Dem, and reference voltages Vref, V1, V2, where: the dimming signal processing unit 202 generates a dimming reference voltage Vdim based on the dimming control signal DIM and the reference voltage Vref; the sampling unit 204 and the detection unit 208 generate a current sampling signal CS _ smp and a current amplification signal CS _ sen, respectively, based on the current detection signal CS; the error amplifier 206 and the capacitor C201 both generate a compensation control signal CMP based on the dimming reference voltage Vdim and the current sampling signal CS _ smp; the clamping unit 212 generates a clamping control signal (not shown in the figure) based on the compensation control signal CMP and a reference voltage V2, wherein the reference voltage V2 is used for down clamping of the compensation control signal CMP; the comparator 210 generates a turn-off control signal PWM _ off based on the clamp control signal and the current amplification signal CS _ sen; the Delay signal generation unit 214 generates a time Delay signal Delay based on the dimming reference voltage Vdim, the compensation control signal CMP, the demagnetization detection signal Dem, and the reference voltage V1; the digital unit 216 generates an on control signal PWM _ on based on the demagnetization detection signal Dem and the time Delay signal Delay, and generates a pulse width modulation signal PWM based on the on control signal PWM _ on and the off control signal PWM _ off.
In the control chip 102 for the switching power supply system 100, by controlling the duration of the power switch Q1 in the off state with the reference voltage V1, the problem of insufficient depth of adjustment of the brightness of the LED due to the input offset voltage of the internal circuit of the control chip 102 can be avoided, and by clamping down the compensation control signal CMP with the reference voltage V2, the occurrence of a situation where the detected signal is weak and not easily detected when the brightness of the LED is adjusted deeply in an analog manner can be avoided.
As shown in fig. 2, in some embodiments, the dimming signal processing unit 202 generates the dimming reference voltage Vdim by operating the dimming control signal DIM and the reference voltage Vref and outputs the dimming reference voltage Vdim to the error amplifier 204 for controlling the magnitude of the system output current Iout; the sampling unit 204 generates a current sampling signal CS _ smp by sampling the current detection signal CS and outputs the current sampling signal CS _ smp to the error amplifier 206; the error amplifier 206 generates an error characterization signal (not shown in the figure) by performing error amplification on the dimming reference voltage Vdim and the current sampling signal CS _ sen; the capacitor C201 integrates the error characterization signal, generates a compensation control signal CMP, and outputs the compensation control signal CMP to the clamping unit 212; the clamping unit 212 generates a clamping control signal and outputs the clamping control signal to the comparator 210 by clamping down the compensation control signal CMP, which is clamped at a V2 level when the compensation control signal CMP is less than the reference voltage V2; the detection unit 208 generates a current amplification signal CS _ sen by detecting and amplifying the current detection signal CS and outputs the current amplification signal to the comparator 210; the comparator 210 generates the off control signal PWM _ off and outputs the off control signal PWM _ off to the digital unit 216 by comparing the clamping control signal and the current amplification signal CS _ sen. Here, it should be noted that when the compensation control signal CMP is not less than the reference voltage V2, the clamping control signal is the compensation control signal CMP itself.
As shown in fig. 2, in some embodiments, the delay signal generating unit 214 includes a voltage-current converting circuit 2142, a compensation signal processing circuit 2144, a switch K201, a comparator 2146, and a capacitor C202, wherein: the voltage-current conversion circuit 2162 generates a dimming reference current Idim based on the dimming reference voltage Vdim; the capacitor C202 and the switch K201 both generate a Ramp control signal Ramp based on the demagnetization detection signal Dem and the dimming reference current Idim; the compensation signal processing circuit 2144 generates the delay control signal Vd based on the compensation control signal CMP and the reference voltage V1; the comparator 2146 generates a time Delay signal Delay based on the Ramp control signal Ramp and the Delay control signal Vd. For example, the voltage-current conversion circuit 2142 generates the dimming reference current Idim by voltage-current converting the dimming reference voltage Vdim; the capacitor C202 is coupled to the switch K201, and the switch K201 turns on and off the control of the inverse signal of the demagnetization detection signal Dem (that is, the switch K201 controls the charging of the dimming reference current Idim to the capacitor C202 based on the demagnetization detection signal Dem); when the demagnetization detection signal Dem is at a logic low level, the switch K201 is turned on, the dimming reference current Idim does not charge the capacitor C202, and the voltage on the capacitor C202, that is, the voltage of the Ramp control signal Ramp, is 0V; when the demagnetization detection signal Dem is at a logic high level, the switch K201 is turned off, the dimming reference current Idim charges the capacitor C202, and the voltage on the capacitor C202, that is, the voltage of the Ramp control signal Ramp, is greater than 0V; the compensation signal processing circuit 2144 generates the delay control signal Vd by operating the voltage of the compensation control signal CMP and the reference voltage V1; the comparator 2146 generates a time Delay signal Delay by comparing the Ramp control signal Ramp and the Delay control signal Vd.
In the constant current control module 1026 shown in fig. 2, the dimming reference voltage Vdim has a high level and a low level corresponding to the magnitude of the system output current Iout, that is, when the dimming reference voltage Vdim is high, the system output current Iout is large; when the dimming reference voltage Vdim is low, the system output current Iout is small. The compensation control signal CMP is an output signal of the error amplifier 206, and the voltage variation of the compensation control signal CMP is the same as the variation direction of the dimming reference voltage Vdim. The voltage of the compensation control signal CMP becomes high when the dimming reference voltage Vdim becomes high, and becomes low when the dimming reference voltage Vdim becomes low.
The operation of the constant current control module 1026 shown in fig. 2 is divided into three phases with the variation of the dimming reference voltage Vdim (or the compensation control signal CMP):
when the system output current Iout is large, the voltage of the compensation control signal CMP is larger than the reference voltage V1, the switching power supply system 100 operates in a quasi-resonant (QR) mode, and the dimming control signal DIM regulates the system output current Iout by controlling the peak current flowing through the inductor L1. In the switching power supply system 100 shown in fig. 1, the current detection signal CS is used to characterize the inductor current IL flowing through the inductor L1, the peak voltage of the current detection signal CS corresponds to the peak current flowing through the inductor L1, and the peak voltage of the current detection signal CS is controlled by the compensation control signal CMP. The time Delay signal Delay is generated by comparing the voltage of the capacitor C202, i.e. the Ramp control signal Ramp and the Delay control signal Vd, and since the voltage of the compensation control signal CMP is greater than the reference voltage V1, and the Delay control signal Vd generated by the compensation signal processing circuit 2144 is 0V, the Delay time of the time Delay signal Delay is also 0, which makes the switching power supply system 100 operate in the QR mode.
When the system output current Iout is small, the voltage of the compensation control signal CMP is greater than the reference voltage V2 and less than the reference voltage V1, the switching power supply system 100 operates in the Discontinuous Conduction Mode (DCM), and the dimming control signal DIM regulates the system output current Iout by controlling the peak current flowing through the inductor L1 and the time Delay signal Delay. In the constant current control module 1026 shown in fig. 2, the operation control of the compensation signal processing circuit 2144 satisfies equation 1:
V d ＝k×(V 1 -V CMP ) <equation 1>
Where k is a designed fixed coefficient. Fig. 3 shows an exemplary circuit diagram of the compensating signal processing circuit 2144 shown in fig. 2, where the resistances of the resistors R301 and R302 are a fixed ratio (R301 is set to R302 in fig. 3), the mirror current ratio of the current mirrors M303 and M304 is 1, and the mirror current ratio of the current mirrors M305 and M306 is also 1, so that the voltage of the delay control signal Vd can be obtained by equation 2:
Figure BDA0003658665660000071
where R303/R301 corresponds to k in equation 1, which is a fixed value.
That is, the compensation signal processing circuit 2144 generates the delay control signal Vd by scaling the difference between the voltage of the compensation control signal CMP and the reference voltage V1.
When the system output current Iout is smaller, the voltage of the compensation control signal CMP is equal to the reference voltage V2, the switching power supply system 100 operates in the Discontinuous Conduction Mode (DCM), and the compensation control signal CMP is clamped at the V2 level by the clamping unit 212, so that the system output current Iout cannot be adjusted, and the minimum voltage of the compensation control signal CMP is set to control the minimum peak current flowing through the inductor L1 during dimming, so as to ensure that the control related detection signal can be detected. At this stage, the voltage of the delay control signal Vd is also fixed at k × V2, but as the dimming reference voltage Vdim becomes lower, the dimming reference current Idim generated by the voltage-current conversion circuit 2142 based on the dimming reference voltage Vdim becomes smaller as shown in equation 3:
Figure BDA0003658665660000081
where Rdim is an equivalent resistance value of the voltage-current conversion circuit 2142 for converting the dimming reference voltage Vdim into the dimming reference current Idim, and the Delay time Td corresponding to the time Delay signal Delay increases as the dimming control voltage Vdim decreases, so that a deeper degree of dimming control can be achieved (i.e., the brightness of the LED can be adjusted more deeply). Fig. 4 shows an operation waveform diagram of a plurality of signals in the constant current control module 1026 shown in fig. 2, where Ton represents a duration time during which the power switch Q1 is in an on state, Toff represents a duration time during which the power switch Q1 is in an off state, Tdem represents a duration time during which the inductor L1 is in a demagnetization state, and Td represents a delay time from a time when the power switch Q1 changes from the off state to the on state to a time when the inductor L1 finishes demagnetization.
In the switching power supply system 100 shown in fig. 1, the dimming control signal DIM may be an analog voltage signal or a PWM pulse signal, and for deep dimming applications, the dimming control signal DIM is usually a PWM pulse signal, which is convenient for a control chip in the switching power supply system for dimmable LED lighting to perform precise control.
Fig. 5 illustrates an example circuit diagram of the dimming signal processing unit 202 illustrated in fig. 2. As shown in fig. 5, the dimming signal processing unit 202 includes an amplifier U501, switches K501 and K502, a resistor R501, a capacitor C501, and an inverter U502, wherein: the positive input end of the amplifier U501 is connected with the reference voltage Vref, the negative input end and the output end of the amplifier U501 are connected to form a buffer structure, and the output end of the amplifier U501 is connected with the switch K501; one end of the switch K501 is connected with the output end of the amplifier U501, and the other end of the switch K501 is connected with the switch K502 and the resistor R501; the control signal of the switch K501 is a dimming control signal DIM, when the dimming control signal DIM is at a logic high level, the switch K501 is in a conducting state, and when the dimming control signal DIM is at a logic low level, the switch K501 is in a switching-off state; one end of the switch K502 is connected with the switch K501 and the resistor R501, and the other end is connected with the ground; the control signal of the switch K502 is an output signal obtained by inverting the phase of the dimming control signal DIM by the inverter U502, when the dimming control signal DIM is at a logic low level, the switch K502 is in a conducting state, and when the dimming control signal DIM is at a logic high level, the switch K502 is in a switching-off state; the switches K501 and K502 are alternately turned on in one pulse period of the dimming control signal DIM; one end of a resistor R501 is connected with the switches K501 and K502, and the other end of the resistor R501 is connected with a capacitor C501 and a dimming reference voltage Vdim; the capacitor C501 has one end connected to the resistor R501 and the dimming reference voltage Vdim, and has one end connected to ground. In the dimming signal processing unit 202, chopping the reference voltage Vref by controlling the on and off of the switches K501 and K502 with the dimming control signal DIM and its inverted logic signal, generating a chopped reference voltage Vchop; the dimming reference voltage Vdim is generated by filtering the chopped reference voltage Vchop by a low-pass filter formed by the resistor R501 and the capacitor C501 together. In other words, the dimming signal processing unit 202 generates the dimming reference voltage Vdim by multiplying the duty ratio of the dimming control signal DIM by the reference voltage Vref as shown in equation 4:
V dim ＝Duty×V ref <equation 4>
Fig. 6 illustrates an example circuit diagram of the digital cell 216 shown in fig. 2. As shown in fig. 6, the digital unit 216 may output the pulse width modulation signal PWM based on the turn-off control signal PWM _ off, the demagnetization detection signal Dem, and the time Delay signal Delay, so that the constant current control module 1026 shown in fig. 2 is controlled according to the timing logic shown in fig. 4.
The control chip and the control method for the switching power supply system according to the embodiment of the invention are not limited to the switching power supply system adopting the BUCK architecture, and are also applicable to the switching power supply systems adopting other architectures, such as fly-back, BOOST, BUCK-BOOST and the like, and only the control of the current detection signal CS and the constant current control module needs to be adjusted correspondingly.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. For example, the algorithms described in the specific embodiments may be modified without departing from the basic spirit of the invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (21)

1. A control chip for a switching power supply system, wherein the switching power supply system comprises an inductor and a power switch, the control chip being configured to:
generating a turn-off control signal for controlling the power switch to change from an on state to an off state based on a dimming control signal for adjusting brightness of the light emitting diode, a current detection signal for characterizing an inductor current flowing through an inductor, and a first reference voltage;
generating an on control signal for controlling the power switch to change from an off state to an on state based on the dimming control signal, the current detection signal, a demagnetization detection signal for representing a demagnetization condition of the inductor, and a second reference voltage; and
generating a pulse width modulation signal for controlling on and off of the power switch based on the off control signal and the on control signal, wherein
The first reference voltage is used for controlling the magnitude of the system output current of the switching power supply system, and the second reference voltage is used for controlling the duration time of the power switch in the off state.
2. The control chip of claim 1, further configured to:
generating a dimming reference voltage based on the dimming control signal and the first reference voltage;
generating a current sampling signal and a current amplifying signal based on the current detection signal;
generating a compensation control signal based on the dimming reference voltage and the current sampling signal;
generating a clamp control signal based on the compensation control signal and a third reference voltage, wherein the third reference voltage is used for lower clamping of the compensation control signal; and
generating the turn-off control signal based on the clamping control signal and the current amplification signal.
3. The control chip of claim 2, further configured to:
generating the dimming reference voltage by multiplying a duty ratio of the dimming control signal by the first reference voltage.
4. The control chip of claim 2, further configured to:
generating the current sampling signal by sampling the current detection signal;
generating an error characterization signal by performing error amplification on the current sampling signal and the dimming reference voltage;
generating the compensation control signal by integrating the error amplification signal;
generating the clamping control signal by clamping down the compensation control signal with the third reference voltage.
5. The control chip of claim 2, further configured to:
generating the current amplification signal by detecting and amplifying the current detection signal;
generating the turn-off control signal by comparing the current amplification signal and the clamp control signal.
6. The control chip of claim 2, further configured to:
generating a dimming reference current based on the dimming reference voltage;
generating a ramp control signal based on the demagnetization detection signal and the dimming reference current;
generating a delay control signal based on the compensation control signal and the second reference voltage;
generating a time delay signal based on the ramp control signal and the delay control signal;
and generating the conduction control signal based on the time delay signal and the demagnetization detection signal.
7. The control chip of claim 6, further configured to:
generating the dimming reference current by voltage-current converting the dimming reference voltage.
8. The control chip of claim 6, further configured to:
and controlling the dimming reference current to charge a capacitor based on the demagnetization detection signal to generate the slope control signal.
9. The control chip of claim 6, further configured to:
generating the delay control signal by scaling a difference between a voltage of the compensation control signal and the second reference voltage.
10. The control chip of claim 6, further configured to:
and generating the conduction control signal by comparing the time delay signal with the demagnetization detection signal.
11. A control method for a switching power supply system, wherein the switching power supply system includes an inductor and a power switch, the control method comprising:
generating a turn-off control signal for controlling the power switch to change from an on state to an off state based on a dimming control signal for adjusting brightness of the light emitting diode, a current detection signal for characterizing an inductor current flowing through an inductor, and a first reference voltage;
generating an on control signal for controlling the power switch to be changed from an off state to an on state based on the dimming control signal, the current detection signal, a demagnetization detection signal for representing the demagnetization condition of the inductor, and a second reference voltage; and
generating a pulse width modulation signal for controlling on and off of the power switch based on the off control signal and the on control signal, wherein
The first reference voltage is used for controlling the magnitude of the system output current of the switching power supply system, and the second reference voltage is used for controlling the duration time of the power switch in the off state.
12. The control method of claim 11, wherein the process of generating the shutdown control signal comprises:
generating a dimming reference voltage based on the dimming control signal and the first reference voltage;
generating a current sampling signal and a current amplifying signal based on the current detection signal;
generating a compensation control signal based on the dimming reference voltage and the current sampling signal;
generating a clamp control signal based on the compensation control signal and a third reference voltage, wherein the third reference voltage is used for lower clamping of the compensation control signal; and
generating the turn-off control signal based on the clamping control signal and the current amplification signal.
13. The control method of claim 12, wherein the dimming reference voltage is generated by multiplying a duty cycle of the dimming control signal by the first reference voltage.
14. The control method of claim 12, wherein the process of generating the shutdown control signal further comprises:
generating the current sampling signal by sampling the current detection signal;
generating an error characterization signal by performing error amplification on the current sampling signal and the dimming reference voltage;
generating the compensation control signal by integrating the error amplification signal;
generating the clamping control signal by clamping down the compensation control signal with the third reference voltage.
15. The control method of claim 12, wherein the process of generating the shutdown control signal further comprises:
generating the current amplification signal by detecting and amplifying the current detection signal;
generating the turn-off control signal by comparing the current amplification signal and the clamp control signal.
16. The control method of claim 12, wherein the process of generating the turn-on control signal comprises:
generating a dimming reference current based on the dimming reference voltage;
generating a ramp control signal based on the demagnetization detection signal and the dimming reference current;
generating a delay control signal based on the compensation control signal and the second reference voltage;
generating a time delay signal based on the ramp control signal and the delay control signal;
and generating the conduction control signal based on the time delay signal and the demagnetization detection signal.
17. The control method of claim 16, wherein the dimming reference current is generated by voltage-current converting the dimming reference voltage.
18. The control method of claim 16, wherein the ramp control signal is generated by controlling the dimming reference current to charge a capacitance based on the demagnetization detection signal.
19. The control method of claim 16, wherein the delay control signal is generated by scaling a difference between the voltage of the compensation control signal and the second reference voltage.
20. The control method according to claim 16, wherein the on control signal is generated by comparing the time delay signal and the demagnetization detection signal.
21. A switching power supply system comprising the control chip of any one of claims 1 to 10.
CN202210567260.1A 2022-05-24 2022-05-24 Switching power supply system and control chip and control method thereof Pending CN115037154A (en)

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