CN111182684A - Non-stroboscopic LED drive circuit compatible with silicon controlled rectifier dimmer - Google Patents
Non-stroboscopic LED drive circuit compatible with silicon controlled rectifier dimmer Download PDFInfo
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Abstract
The invention discloses a stroboflash-free LED driving circuit compatible with a silicon controlled rectifier dimmer, which comprises a rectifier bridge, a functional block M1, an external power device Q1, an external ground voltage division network formed by connecting a resistor RU and a resistor RD in series, an isolating diode D1, an electrolytic capacitor Cd, a charging current detection resistor R2, an LED load string and an LED output current detection resistor R3. The invention ensures that the corresponding input mains supply instantaneous voltage is greater than the voltage on the electrolytic capacitor when the silicon controlled dimmer is switched on by controlling and adjusting the product of the starting voltage before the silicon controlled dimmer is switched on and the volt-second product of the two ends of the corresponding silicon controlled dimmer, thereby ensuring that the silicon controlled dimmer is reliably switched on.
Description
Technical Field
The invention relates to an LED drive circuit, in particular to a stroboflash-free LED drive circuit compatible with a silicon controlled rectifier dimmer.
Background
In order to enable the output of the triac-dimmable LED driving circuit to be free of strobing, considering that there is no input power before the triac dimmer conducts in a phase-cut manner, an energy storage element is required to store energy to ensure that the energy of the energy storage element provides stable driving current for the LED load through the driving circuit before the triac dimmer conducts in the phase-cut manner. Typically this energy storage element is an electrolytic capacitor. How to ensure that the electrolytic capacitor can be charged by mains supply through the thyristor dimmer in each half cycle is the focus of the present invention.
For the electrolytic capacitor energy storage element, the silicon controlled dimmer is required to work normally, and has two requirements: firstly, according to the dimming angle of the silicon controlled dimmer, due to the requirement of a corresponding R-C trigger circuit in the silicon controlled dimmer, the conduction of the silicon controlled dimmer is ensured by the accumulation of voltage and time at two ends of the silicon controlled dimmer at a corresponding set R-C time constant, namely the silicon controlled dimmer is ensured to be conducted by the corresponding volt-second product; and to make the thyristor conduct at the moment, the corresponding instantaneous voltage of the mains supply must be greater than the voltage on the electrolytic capacitor of the energy storage element. Second, the current flowing through the triac dimmer must be guaranteed to be greater than the required holding current. Obviously, the requirement is to ensure that the silicon controlled rectifier dimmer can be normally switched on; the second requirement is to ensure that the thyristor dimmer can be continuously conducted. Only if the requirements of the two points are met, the silicon controlled rectifier dimmer can normally work with the LED drive circuit without stroboflash.
The invention patent of publication No. CN110035579A, high power factor non-stroboscopic linear control method and control device thereof compatible with silicon controlled dimmer, the control device structure and control scheme thereof, comprises a function block M1, a Q1 power MOSFET, a resistor R1 and a resistor R2 which are connected in series to form an external ground voltage-dividing network; the function block M1 controls an internal ground voltage control current source Is and an internal ground voltage control current source Io according to the DIM signal waveform; the gate of the Q1 power MOSFET is controlled by resistance Rc and functional block M1; the voltage at two ends of the internal ground voltage control current source Io of the functional block M1 is output by an internal voltage division network, and the FB signal voltage is internally fed back to the functional block M1.
The invention patent of publication No. CN106888524A, LED driving circuit with thyristor dimmer, circuit module and control method, controls the dc bus voltage to change in a predetermined manner through the bleeder circuit before the thyristor dimmer is turned on, so as to avoid the influence of inconsistent leakage current on the turn-on point of the thyristor dimmer caused by different types of thyristor dimmers and different circuit settings, thereby avoiding the problem of LED flickering. Meanwhile, the voltage of the silicon controlled dimmer after being conducted can be influenced by controlling the voltage of the direct current bus, so that the voltage of a conducting point can be flexibly set according to the requirement. But the output has a strobe problem.
The invention patent of publication No. CN107995750A, "circuit module, dimmable LED driving circuit and control method" can push back the on-time when the on-angle is large by controlling the dc bus voltage during the discharging to be constant and making the expected value of the dc bus voltage adjustable. When the thyristor dimmer is switched on, the direct-current bus voltage can be positioned near the lighting voltage, and the direct-current bus voltage does not need to be discharged for a long time after the thyristor dimmer is switched on. Therefore, the system loss is effectively reduced, and the system efficiency is improved. But the output has a strobe problem.
Accordingly, there is a need for improvements in the art. The problems of low efficiency, stroboscopic output and the like under the requirements of compatibility and high power factor of the silicon controlled rectifier dimmer in the conventional linear silicon controlled rectifier dimming scheme can be overcome.
Disclosure of Invention
The invention aims to provide an efficient non-stroboscopic LED driving circuit compatible with a silicon controlled rectifier dimmer and a corresponding control scheme.
In order to solve the technical problem, the invention discloses a flicker-free LED driving circuit compatible with a silicon controlled dimmer, which comprises a rectifier bridge, a functional block M1, an external power device Q1, an external ground voltage division network formed by connecting resistors RU and RD in series, an isolating diode D1, an electrolytic capacitor Cd, a charging current detection resistor R2 (detection resistor R2 for short), an LED load string and an LED output current detection resistor R3 (detection resistor R3 for short);
the mains supply is supplied to a rectifier bridge through a silicon controlled dimmer TRIAC, the negative end of the output voltage of the rectifier bridge is grounded, and the positive end of the output voltage of the rectifier bridge is respectively connected with the following components: an external ground voltage division network formed by connecting resistors RU and RD in series, an HV _ I pin of a functional block M1, an HV _ C pin of a functional block M1 and an electrode I of an external power device Q1 after an Rc resistor; the pole III of the external power device Q1 is connected with the HV _ C pin and the Rc resistor of the functional block M1; the pole II of the external power device Q1 is connected with the anode of an isolation diode D1; the cathode of the isolating diode D1 is connected with the positive end LED + of the LED load string and the positive end of the electrolytic capacitor Cd(ii) a The negative end of the electrolytic capacitor Cd is grounded through a charging current detection resistor R2; a connecting line of the electrolytic capacitor Cd and the charging current detection resistor R2 is connected with a CSCAP pin of the functional block M1; the LED load string negative terminal LED-is connected with the LED-pin of the functional block M1, and the Cs pin of the functional block M1 is grounded through an LED output current detection resistor R3; the CSPULL pin of the functional block M1 and the external resistor R1 form an internal voltage-controlled current source IVCONT(ii) a A DIM pin of the functional block M1 is connected to a connection line of the resistors RU and RD (that is, an output of the external ground voltage division network formed by the resistors RU and RD in series is DIM); the GND pin of the functional block M1 is connected with the output voltage negative terminal of the rectifier bridge and the ground; information on the current flowing through the charging current detection resistor R2 and the LED output current detection resistor R3 is fed back to the function block M1 in the form of voltage.
The compatible silicon controlled dimmer is an improvement of a stroboflash-free LED driving circuit: the external power device Q1 is a power MOS tube;
the positive ends of the output voltages of the rectifier bridges are respectively connected with the following components: an external ground voltage division network formed by connecting resistors RU and RD in series, an HV _ I pin of a functional block M1, an HV _ C pin of a functional block M1 and a drain electrode of an external power device Q1 after an Rc resistor;
the source of the external power device Q1 is connected with the anode of an isolation diode D1;
the gate of external power device Q1 is connected to pin HV _ C and Rc resistor of functional block M1.
The compatible silicon controlled rectifier dimmer does not have another improvement of stroboscopic LED drive circuit as the invention: the external power device Q1 is a power PNP triode;
the positive ends of the output voltages of the rectifier bridges are respectively connected with the following components: an external ground voltage division network formed by connecting resistors RU and RD in series, an HV _ I pin of a functional block M1, an HV _ C pin of a functional block M1 and an emitter of an external power device Q1 after an Rc resistor;
the collector of the external power device Q1 is connected with the anode of an isolation diode D1;
the base of the external power device Q1 is connected to HV _ C pin and Rc resistor of the functional block M1.
The compatible silicon controlled dimmer non-stroboscopic LED driving circuit is further improved as follows:
the function block M1 is provided with the following 8 pins respectively: HV _ C pin, HV _ I pin, DIM pin, CSPULL pin, GND pin, Cs pin, CSCAP pin, LED-pin;
the function block M1 comprises a peak value detection module, a VF generator module, a comparator 1 module and an accumulator 1+ DAC1 module which are connected in sequence by signals; the peak value detection module outputs Vpeak to the VF generator module, and the VF generator module outputs VFThe comparator 1 module and the comparator 1 module output corresponding addition and subtraction logic signals to the accumulator 1+ DAC1 module;
the DIM pin is respectively connected with the peak value detection module, the comparator 1 module, the comparator 2 module and the error amplifier 1 module;
the accumulator 1+ DAC1 module outputs VCONT to the comparator 2 module, the comparator 2 module outputs a zero-crossing logic signal (zero-crossing signal) and a clock logic signal (clock) corresponding to the on-jump of the TRIAC dimmer according to the input DIM and VCONT signals, the clock logic signal is simultaneously transmitted to the accumulator 1+ DAC1 module, the accumulator 2+ DAC2 module, the valley comparison module, the error amplifier 2 module, and the error amplifier 1 module, and the accumulation operations of the accumulator 1+ DAC1 module and the accumulator 2+ DAC2 module are controlled by the clock logic signal;
the input of the error amplifier 1 module is DIM, Vlevel analog signals, zero-crossing logic signals and clock logic signals; the clock logic signal and the zero-crossing logic signal respectively control the error amplifier 1 module to start working and reset; according to DIM and Vlevel analog signals, the error amplifier 1 module outputs control signals to the voltage-controlled current source I1 and the voltage-controlled current source I2 respectively; the positive end of the voltage-controlled current source I1 is connected with the normally-open end of the switch, and the negative end of the voltage-controlled current source I1 is connected with the CSPULL pin; the normally closed end of the switch is connected with an HV _ I pin, the HV _ I pin is connected with the positive end of a voltage-controlled current source I2, and the negative end of the voltage-controlled current source I2 is grounded; the combination of the voltage controlled current source I1 and the voltage controlled current source I2 forms an internal voltage controlled current source IVCONT；
The two inputs of the valley value comparison module are respectively the voltage and the preset value V on the LED output current source fed back by the LED-pinVal(ii) a Tool of valley comparison moduleA clock logic signal controlled by the output of the comparator 2 module is made; the valley value comparison module outputs corresponding addition and subtraction logic signals to the accumulator 2+ DAC2 module, and the accumulator 2+ DAC2 module outputs LED-REF to the error amplifier 3 module;
the positive end of the voltage-controlled current source I3 is connected with the LED-pin, and the negative end of the voltage-controlled current source I3 is connected with the Cs pin; the control end of the voltage-controlled current source I3 is connected with the output of the error amplifier 3 module; the error amplifier 3 module controls the control end of the voltage-controlled current source I3 according to the input LED-REF signal and the feedback signal output provided by the Cs pin, so that the output current of the voltage-controlled current source I3 is equal to LED-REF/R3;
the positive end of the voltage-controlled current source I4 is connected with the HV _ C pin, and the negative end of the voltage-controlled current source I4 is connected to the ground; the control end of the voltage-controlled current source I4 is controlled by the output of the error amplifier 2 module; the error amplifier 2 module is based on the input fixed analog quantity VCHA-REFThe output current of the voltage-controlled current source I4 is controlled by a feedback signal provided by a CSCAP pin and a clock logic signal output by the comparator 2 module, so that the output current controls the input current of an external power device Q1 through an external resistor Rc, and the charging current of an electrolytic capacitor Cd is equal to VCHA-REF/R2。
The compatible silicon controlled dimmer non-stroboscopic LED driving circuit is further improved as follows:
the function block M1 finds a proper reference voltage VCONT according to a voltage division network feedback voltage signal DIM formed by RU and RD to ensure that the instantaneous voltage of the mains supply is greater than the valley voltage of the electrolytic capacitor Cd when the silicon controlled dimmer TRIAC is switched on;
by means of the accumulator 1+ DAC1 module generating the reference voltage VCONT by the peak detection module in the functional block M1, the comparator 1 module, the comparator 2 module, the internal voltage controlled current source IIVCONTAnd the output voltage of the rectifier bridge form a regulating loop.
The compatible silicon controlled dimmer non-stroboscopic LED driving circuit is further improved as follows:
the function block M1, an external power device Q1, an electrolytic capacitor Cd, a detection resistor R2, an isolation diode D1, a rectifier bridge, a silicon controlled dimmer TRIAC and a mains supply form an electrolytic capacitor Cd charging control loop; and controlling the amplitude of the charging current of the electrolytic capacitor Cd to be larger than the holding current of the silicon controlled dimmer TRIAC.
The compatible silicon controlled dimmer non-stroboscopic LED driving circuit is further improved as follows:
the function block M1, the LED load, the electrolytic capacitor Cd and the LED output current detection resistor R3 form an output LED current control loop, and the output LED current of the output LED current control loop is the valley voltage V of the electrolytic capacitor CdCd_VALAnd (5) controlling.
The technical advantages of the non-stroboscopic LED driving circuit compatible with the silicon controlled rectifier dimmer are as follows:
1. the size of the product of the starting voltage before the silicon controlled dimmer is switched on and the volt-second voltage corresponding to the two ends of the silicon controlled dimmer can be controlled and adjusted to ensure that the corresponding input mains supply instantaneous voltage is greater than the upper voltage of the electrolytic capacitor when the silicon controlled dimmer is switched on, so that the silicon controlled dimmer is reliably switched on.
2. The charging current of the electrolytic capacitor is controlled to be larger than the holding current of the silicon controlled dimmer to ensure that the silicon controlled dimmer can be continuously conducted; thus, the input power is controlled by controlling the amplitude and the width of the charging pulse current of the electrolytic capacitor; the conduction angle of the thyristor dimmer controls the pulse width of the charging pulse current, thereby controlling the magnitude of the input power.
3. The valley voltage of the electrolytic capacitor controls the current of the corresponding output LED; the valley voltage of the electrolytic capacitor controls the current of the output LED, namely the output power and ensures that the valley voltage of the electrolytic capacitor is always slightly larger than the load voltage of the LED; therefore, the input and output power balance is achieved, and the output LED light is enabled to obtain the efficiency as high as possible without stroboflash.
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
FIG. 1 shows two types of LED driving circuits without stroboscopic effect for compatible silicon controlled dimmer;
wherein,
FIG. 1.a is a circuit diagram of a non-stroboscopic LED driving circuit using a power MOS tube compatible silicon controlled dimmer;
FIG. 1.b is a non-stroboscopic LED driving circuit using a power PNP triode compatible silicon controlled dimmer;
fig. 2 is a schematic diagram of the peak detection circuit within the functional block M1 outputting the peak voltage VPEAK minus Δ V to obtain the valve level VF;
fig. 3 is a block diagram of the inside of the function block M1.
Detailed Description
The invention will be further described with reference to specific examples, but the scope of the invention is not limited thereto:
fig. 1.a and fig. 1.b are two forms of compatible silicon controlled dimmer non-stroboscopic LED driving circuit, namely, a power MOS transistor and a power PNP triode are respectively used as external power devices.
The method comprises the following specific steps:
embodiment 1, a compatible silicon controlled rectifier dimmer does not have stroboscopic LED drive circuit, use power MOS pipe as external power device Q1, as shown in fig. 1. a;
the stroboflash-free LED driving circuit compatible with the silicon controlled rectifier dimmer comprises a rectifier bridge, a functional block M1, an external power device Q1, an external ground voltage division network formed by connecting a resistor RU and a resistor RD in series, an isolation diode D1, an electrolytic capacitor Cd, a charging current detection resistor R2 (detection resistor R2 for short), an LED load string and an LED output current detection resistor R3 (detection resistor R3 for short).
The mains supply is supplied to a rectifier bridge through a silicon controlled dimmer TRIAC, the negative end of the output voltage of the rectifier bridge is grounded, and the positive end of the output voltage of the rectifier bridge is respectively connected with the following components: an external ground voltage division network formed by connecting resistors RU and RD in series, an HV _ I pin of a functional block M1, an HV _ C pin of a functional block M1 and a drain electrode of an external power device Q1 (figure 1.a) after an Rc resistor; the gate of the external power device Q1 is connected with the pin HV _ C and the Rc resistor of the functional block M1; the source of the external power device Q1 is connected with the anode of an isolation diode D1; the negative electrode of the isolating diode D1 is connected with the positive end LED + of the LED load string and the positive end of the electrolytic capacitor Cd; the negative end of the electrolytic capacitor Cd is grounded through a detection resistor R2; a connecting line of the electrolytic capacitor Cd and the detection resistor R2 is connected with a CSCAP pin of the functional block M1; LED load string negative terminal LED-is in phase with LED-pin of function block M1In turn, the Cs pin of block M1 goes to ground through sense resistor R3. The CSPULL pin of the functional block M1 and the external resistor R1 form an internal voltage-controlled current source IVCONT. A DIM pin of the functional block M1 is connected with a connection line of the resistors RU and RD; namely, the output of an external ground voltage division network formed by connecting the resistors RU and RD in series is DIM; the GND pin of the functional block M1 is connected with the output voltage negative terminal of the rectifier bridge and the ground; information on the current flowing in R2 and R3 is fed back to the function block M1 in the form of voltage.
The function block M1 is as described in fig. 3:
the function block M1 is provided with the following 8 pins respectively: HV _ C pin, HV _ I pin, DIM pin, CSPULL pin, GND pin, Cs pin, CSCAP pin, LED-pin;
the function block M1 comprises a peak detection module, a VF generator module, a comparator 1 module and an accumulator 1+ DAC1 module which are connected in sequence by signals, wherein the peak detection module outputs Vpeak to the VF generator module, and the VF generator module outputs VFThe comparator 1 module and the comparator 1 module output corresponding addition and subtraction logic signals to the accumulator 1+ DAC1 module;
the DIM pin is respectively connected with the peak value detection module, the comparator 1 module, the comparator 2 module and the error amplifier 1 module;
the accumulator 1+ DAC1 module outputs VCONT to the comparator 2 module, and the comparator 2 module outputs a zero-crossing logic signal (zero-crossing signal) and a clock logic signal (clock) corresponding to the TRIAC dimmer TRIAC conduction jump-up according to the input DIM and VCONT signals, the clock logic signal being simultaneously transmitted to the accumulator 1+ DAC1 module, the accumulator 2+ DAC2 module, the valley comparison module, the error amplifier 2 module, and the error amplifier 1 module; the accumulation operations of the accumulator 1+ DAC1 module and the accumulator 2+ DAC2 module are controlled by the clock logic signal.
The input of the error amplifier 1 module is DIM, Vlevel analog signals, zero-crossing logic signals and clock logic signals; the clock logic signal and the zero-crossing logic signal respectively control the error amplifier 1 module to start working and reset; according to the two input DIM and Vlevel analog signals, the error amplifier 1 module outputs control signals to the voltage-controlled current source I1 and the voltage-controlled current source I2 respectively; positive terminal of voltage-controlled current source I1The negative end of the voltage-controlled current source I1 is connected with the CSPULL pin; the normally closed end of the switch is connected with an HV _ I pin, the HV _ I pin is connected with the positive end of a voltage-controlled current source I2, and the negative end of the voltage-controlled current source I2 is grounded; the combination of the voltage controlled current source I1 and the voltage controlled current source I2 forms an internal voltage controlled current source IVCONT。
Two analog inputs of the valley comparison module are respectively the voltage on the LED output current source fed back by the LED-pin and the preset value VVal(ii) a The valley value comparison module is controlled by a clock logic signal output by the comparator 2 module; the valley value comparison module outputs corresponding addition and subtraction logic signals to the accumulator 2+ DAC2 module, and the accumulator 2+ DAC2 module outputs LED-REF to the error amplifier 3 module;
the positive end of the voltage-controlled current source I3 is connected with the LED-pin, and the negative end of the voltage-controlled current source I3 is connected with the Cs pin; the control end of the voltage-controlled current source I3 is connected with the output of the error amplifier 3 module; the error amplifier 3 module controls the control terminal of the voltage controlled current source I3 according to the input LED-REF signal and the feedback signal output provided by the Cs pin so that the output current of the voltage controlled current source I3 is exactly equal to LED-REF/R3.
The positive end of the voltage-controlled current source I4 is connected with the HV _ C pin, and the negative end of the voltage-controlled current source I4 is connected to the ground; the control end of the voltage-controlled current source I4 is controlled by the output of the error amplifier 2 module; the error amplifier 2 module is based on the input fixed analog quantity VCHA-REFThe output current of the voltage-controlled current source I4 is controlled by a feedback signal provided by a CSCAP pin and a clock logic signal output by the comparator 2 module, so that the output current controls the input current of the external power device Q1 through an external resistor Rc, namely the charging current of an electrolytic capacitor Cd is exactly equal to VCHA-REF/R2。
The following tasks are completed:
firstly, the function block M1 finds a suitable reference voltage VCONT according to the voltage division network feedback voltage signal DIM formed by RU and RD to ensure that the instantaneous voltage of the mains is greater than the valley voltage of the electrolytic capacitor Cd when the TRIAC is turned on. Peak detection module, accumulator 1+ DAC1 module generating reference voltage VCONT, comparator 1 module, comparator 2 module, internal voltage controlled current source I in functional block M1VCONTAnd the output voltage of the rectifier bridge form a regulating loop to participate in the task.
The method specifically comprises the following steps: the function block M1 responds to the instantaneous mains voltage V when the TRIAC is switched on according to this cycleIN(t) iteratively adjusting and outputting the reference voltage VCONT required to be controlled in the next period. When the DIM feedback voltage rises to the existing reference voltage VCONT, the comparator 2 module and the error amplifier 1 module turn on the internal voltage-controlled current source IVCONTThereby, the voltage at the two ends of the controlled silicon dimmer TRIAC is started and controlled to be integrated with respect to time, namely the corresponding volt-second product, so that the controlled silicon dimmer TRIAC is conducted; by internal voltage control of current source IVCONTTo adjust voltage waveform V corresponding to DIM feedback voltageLEVELI.e. to make the rectifier bridge output voltage follow the voltage waveform V before the TRIAC is turned on, as shown in fig. 2LEVELI.e. DIM feedback voltage corresponds to voltage waveform VLEVELInternal voltage-controlled current source I of error amplification regulating block M1 via error amplifier 1VCONTThe output voltage of the rectifier bridge is regulated via the HV _ I pin of the block M1, i.e. by means of an internal voltage-controlled current source IVCONTThe output is regulated so that the voltage V across the TRIAC dimmerSCR(t) is the mains instantaneous voltage VIN(t) subtracting VLEVELNamely:
VSCR(t)＝VIN(t)-VLEVEL(t)
the voltage at the two ends of the TRIAC of the thyristor dimmer is integrated with respect to time, namely the corresponding volt-second product VT (t), and obviously, when the corresponding volt-second product VT (t) is increased to reach the required volt-second product corresponding to the conduction of the TRIAC of the thyristor dimmer, the TRIAC is conducted. The comparator 1 module detects whether the instantaneous voltage of the mains supply reaches a valley voltage V greater than the electrolytic capacitor Cd when the silicon controlled dimmer TRIAC is switched onCd_VALI.e. with VFComparing, the comparator 1 module outputs corresponding addition and subtraction logic signals to the accumulator 1+ DAC1 module, the clock output by the comparator 2 module makes the accumulationThe 1+ DAC1 module output is increased or decreased, thus iteratively adjusting the accumulator 1+ DAC1 module output reference voltage VCONT; that is, to ensure that the instantaneous voltage of the commercial power corresponding to the moment when the silicon controlled dimmer TRIAC is turned on is greater than the valley voltage V of the electrolytic capacitor CdCd_VAL. To iteratively adjust the reference voltage VCONT, function M1 detects V corresponding to the peak voltage of the input rectifier bridge voltage via its internal peak detection modulePEAKThe corresponding valve level voltage V is obtained through a VF generator moduleFThis is caused by the peak voltage VPEAKSubtracting a difference value delta V to obtain; and makes the valve level voltage VFNot less than the valley voltage V of the electrolytic capacitorCd_VALI.e. by
VF＝VPEAK-ΔV≥VCd_VAL
Thus, the instantaneous voltage and V of the mains supply output at the moment of conducting the TRIAC of the silicon controlled dimmer every timeFComparing the voltage with the voltage of the instantaneous voltage of the commercial power output when the silicon controlled rectifier dimmer TRIAC is conductedFWhile, the accumulator 1+ DAC1 module output reference voltage VCONT is decreased; when the instantaneous voltage of the commercial power output by the TRIAC is less than VFWhen the voltage is zero, the accumulator 1+ DAC1 module is increased to output the reference voltage VCONT; the reference voltage VCONT is continuously compared and iteratively adjusted in such a way, so as to ensure that the instantaneous voltage of the mains supply output by the TRIAC is slightly larger than the valley voltage V of the electrolytic capacitorCd_VAL. The regulation reference voltage VCONT varies in response to the volt-second product VT (t) of the TRIAC dimmer.
And secondly, a function block M1, an external power device Q1, an electrolytic capacitor Cd, a detection resistor R2, an isolation diode D1, a rectifier bridge, a silicon controlled dimmer TRIAC and a mains supply form an electrolytic capacitor Cd charging control loop, and the amplitude of the charging current of the electrolytic capacitor Cd is required to be controlled to be larger than the holding current of the silicon controlled dimmer TRIAC. The HV _ C pin of the functional block M1 controls the gate voltage of the external power device Q1 via the external resistor Rc. The HV _ C pin of the functional block M1 is the output of a voltage controlled current source I4. The detection voltage on the detection resistor R2 is fed back to the error amplifier 2 of the functional block M1 through the CSCAP pin of the functional block M1, and the feedback voltage on the resistor R2 and the internally set reference level VCHA_REFControl of voltage control via error amplifier 2 moduleThe current source I4 outputs current, the grid voltage of the external power device Q1 is controlled through the resistor Rc, and therefore the amplitude of the electrolytic capacitor Cd charging pulse current is controlled to be equal to VCHA_REF/R2。
In order to ensure that the commercial power can provide enough proper energy for the electrolytic capacitor Cd through the silicon controlled dimmer TRIAC, the rectifier bridge, the external power device Q1, the isolating diode D1 and the detection resistor R2, the charging current of the electrolytic capacitor Cd must be larger than the holding current of the silicon controlled dimmer TRIAC, and the adjustment of the input power of the electrolytic capacitor Cd is completed by controlling the amplitude and the pulse width of the charging pulse current of the electrolytic capacitor Cd. The amplitude of the electrolytic capacitor Cd charging pulse current is set by a reference level V set inside a functional block M1CHA_REFAnd a sense resistor R2; the pulse width of the charging pulse current of the electrolytic capacitor Cd is determined by the conduction angle of the thyristor dimmer TRIAC and the voltage difference between the output voltage of the rectifier bridge and the voltage on the electrolytic capacitor Cd.
When the conduction angle of the TRIAC dimmer TRIAC is smaller than 150 °, the pulse width of the charging pulse current of the electrolytic capacitor Cd is determined by the following two conditions: 1) the conduction angle of the silicon controlled dimmer TRIAC, 2), and the voltage difference between the output voltage of the rectifier bridge and the voltage on the electrolytic capacitor Cd; that is, the on-time of the TRIAC determines the rising edge of the charging pulse current, and the voltage difference between the output voltage of the rectifier bridge and the voltage across the electrolytic capacitor Cd determines the falling edge of the charging pulse current.
When the conduction angle of the silicon controlled dimmer TRIAC is larger than 150 degrees, the pulse width rising and falling edge of the charging pulse current of the electrolytic capacitor Cd is completely determined by the voltage difference between the output voltage of the rectifier bridge and the voltage on the electrolytic capacitor Cd.
Thirdly, the functional block M1, the LED load, the electrolytic capacitor Cd and the LED output current detection resistor R3 form an output LED current control loop, and the output LED current of the output LED current control loop is the valley voltage V of the electrolytic capacitor CdCd_VALAnd (5) controlling. Because of no stroboflash, the electrolytic capacitor Cd valley voltage VCd_VALMust be greater than the LED load voltage VLEDI.e. input-output power balancing. Electrolytic capacitor valley voltage VCd_VALAnd LED load voltage VLEDThe difference is a voltage VDiffAccording to voltage VDiffWith a predetermined value VVal(VValThe valve voltage value can be 2V or other values, and the corresponding power consumption and efficiency are influenced by the value; the lower this value, the higher the efficiency) error to iteratively adjust the accumulator 2+ DAC2 module output reference voltage LED-REF in block M1.
Valley voltage V of corresponding control electrolytic capacitor CdCd_VALGreater than LED load voltage VLEDThe accumulator 2+ DAC2 module outputs the reference voltage LED-REF as a reference level corresponding to the magnitude of the LED current. The output LED current is fed back to the error amplifier 3 module and the output reference voltage LED-REF error amplification control through the CS pin of the functional block M1 by the detection resistor R3. The conduction angle corresponding to the time constant of the internal trigger circuit of the TRIAC dimmer influences the input power, and naturally influences the output power under the requirement of input and output power balance.
The specific iterative adjustment operation is as follows: valley voltage V of electrolytic capacitor CdCd_VALAnd LED load voltage VLEDDifference voltage VDiffAnd a preset value VValComparing by a valley comparison module if VDiffGreater than a predetermined value VValIncreasing the output reference voltage LED-REF of the accumulator 2+ DAC2 module; if VDiffLess than a predetermined value VValDecreasing the accumulator 2+ DAC2 module output reference voltage LED-REF; the reference voltage LED-REF is continuously compared and iteratively adjusted in such a way that the valley voltage V of the electrolytic capacitor Cd is ensuredCd_VALAnd LED load voltage VLEDDifference voltage VDiffAt a predetermined value VValNearby. Increasing the accumulator 2+ DAC2 module output reference voltage LED-REF means increasing the LED output current, which causes the valley voltage V of the electrolytic capacitor CdCd_VALDecrease; conversely, decreasing the accumulator 2+ DAC2 module output reference voltage LED-REF means decreasing the LED output current, which causes the electrolytic capacitor Cd valley voltage VCd_VALAnd (4) increasing.
Valley voltage V of electrolytic capacitor CdCd_VALInfluenced by its input charging current magnitude and pulse width and output LED current. Because of no stroboflash, the valley voltage V of the electrolytic capacitor is requiredCd_VALMust be greater than the LED load voltage VLEDThat is, the input power of the electrolytic capacitor Cd must be constantly balanced with the output power thereof. The output reference voltage LED-REF of the internal accumulator 2+ DAC2 block in block M1 is used to control the input power to output power balance of the electrolytic capacitor.
The adjustment process of the LED output current along with the conduction angle of the silicon controlled dimmer TRIAC is as follows:
as the conduction angle of the TRIAC dimmer decreases, the charging current pulse width of the electrolytic capacitor Cd decreases, i.e., the input power decreases. Suppose that the electrolytic capacitor Cd at this time has a valley voltage VCd_VALAnd the accumulator 2+ DAC2 module outputs a reference voltage LED-REF and the LED output current is not changed, namely the output power is not changed, and the input power is reduced because the output power is not changed, so that the valley voltage V of the electrolytic capacitor CdCd_VALBeginning to decrease, the valley voltage V of the electrolytic capacitor CdCd_VALAnd LED load voltage VLEDDifference voltage VDiffWith a predetermined value VValAnd the output error of the valley comparator module is iteratively adjusted, the output reference voltage LED-REF of the accumulator 2+ DAC2 module is reduced, so that the output LED current is reduced, the output power is reduced, and the new input and output power balance is achieved. The output LED current thus decreases as the conduction angle of the TRIAC dimmer decreases; conversely, the output LED current thus increases as the conduction angle of the TRIAC dimmer increases.
Because the electrolytic capacitor Cd valley voltage VCd_VALThe LED power supply is always controlled to be slightly larger than the LED load voltage, namely, the power supply can be continuously carried out, and the LED current is possible without stroboflash. The voltage on the LED current source is the voltage on the electrolytic capacitor Cd minus the LED load voltage. The voltage on the LED current source provides a valley voltage V corresponding to the electrolytic capacitor CdCd_VALThis is in good information, which is very advantageous for the function block M1 with LED load, electrolytic capacitor Cd and LED output current control. An analog signal is input to the error amplifier 3 module through a CS pin by the feedback voltage of the detection resistor R3, the analog signal of the reference voltage LED-REF is output by the accumulator 2+ DAC2 module, and the voltage-controlled current source I3 is output by the error amplifier 3 module to form an output LED current control loop so as to ensure the valley value of the electrolytic capacitorVoltage VCd_VALSlightly larger than the LED load voltage, thereby achieving high efficiency.
To accomplish task one, the function block M1 is internally composed of a comparator 1 module, a comparator 2 module, a peak detection module, an error amplifier 1 module, and an internal voltage-controlled current source IVCONTThe accumulator 1+ DAC1 module output reference level VCONT and the rectifier bridge output voltage form a regulation loop. The output voltage regulating loop of the rectifier bridge is a voltage dividing network feedback signal DIM and error amplifier 1 module formed by the output voltage of the rectifier bridge through RU and RD, an accumulator 1+ DAC1 module outputs a reference level VCONT and an internal voltage-controlled current source IVCONTAnd (3) forming. To accomplish task one, two control loops are required to accomplish this. Firstly, outputting a reference level VCONT according to the current accumulator 1+ DAC1 module, when a feedback signal DIM is greater than or equal to the reference level VCONT, starting to control the voltage at two ends of the silicon controlled rectifier dimmer TRIAC to be integrated with respect to time, namely, the voltage is a corresponding volt-second product, namely, the voltage at two ends of the silicon controlled rectifier dimmer TRIAC is controlled to be integrated with respect to time VT (t) before a rectifier bridge output voltage regulating loop ensures the silicon controlled rectifier TRIAC to be switched on; secondly, the corresponding value of the instantaneous voltage of the commercial power at the conduction time of the silicon controlled dimmer TRIAC and the predetermined valve level voltage VFIteratively adjusts the reference level VCONT. This predetermined threshold level voltage VFIs a corresponding voltage greater than the valley voltage V of the electrolytic capacitorCd_VALIn (1). Therefore, the instantaneous voltage of the mains supply is ensured to be close to the equivalent preset voltage value when the silicon controlled dimmer TRIAC is conducted, namely the instantaneous voltage is greater than the valley voltage V of the electrolytic capacitorCd_VAL。
Before the thyristor dimmer TRIAC is turned on, when the feedback signal DIM is greater than or equal to the reference level VCONT, the voltage at the two ends of the thyristor dimmer TRIAC is controlled to integrate with respect to time, that is, to obtain the corresponding volt-second product, and the voltage at the two ends of the thyristor dimmer TRIAC is controlled to integrate with respect to time VT (t), and obviously, when the corresponding volt-second product VT (t) increases to reach the volt-second product required by the thyristor dimmer to be turned on, the thyristor dimmer TRIAC is turned on. In particular, DIM and the corresponding voltage waveform V can be coupled via the error amplifier 1 block of block M1LEVELError amplification and control of voltage-controlled regulation currentSource IVCONTVoltage controlled regulated current I through HV _ I pinVCONTThe output voltage of the rectifier bridge before the TRIAC is conducted is adjusted to be the corresponding voltage waveform VLEVEL。
When the feedback signal DIM is greater than or equal to the reference level VCONT, the output voltage regulating loop of the rectifier bridge is started to correspond to the voltage waveform V according to the output voltage of the rectifier bridgeLEVELSince the control level of the output voltage regulation loop corresponds to the voltage waveform V as shown in FIG. 2LEVELThe voltage-controlled regulating current I of the output voltage regulating loop circuit through HV _ I pinVCONTRapidly adjusting the output voltage of the rectifier bridge from the corresponding reference level VCONT to the corresponding voltage waveform VLEVEL. The voltage at two ends of the TRIAC of the silicon controlled dimmer is VSCR(t)＝VIN(t)-VLEVEL(t) and starting integration until the thyristor dimmer TRIA switches on when the corresponding volt-second product increases to the required volt-second product for the thyristor dimmer to switch on. When the silicon controlled dimmer TRIAC is conducted, if the instantaneous voltage of the commercial power is higher than the predetermined valve level voltage VFI.e. higher than the Cd valley voltage V of the electrolytic capacitorCd_VALThe charging current of the electrolytic capacitor Cd is rapidly established. If the instantaneous voltage of the mains supply is lower than the predetermined threshold level voltage VFVoltage-controlled regulating current source IVCONTA constant current greater than the thyristor holding current is generated to ensure that the thyristor dimmer TRIAC continues to conduct until the electrolytic capacitor Cd charging current is established.
The output voltage of the rectifier bridge is fed back to a signal DIM through a voltage division network formed by RU and RD, and then enters a peak value detection module inside a functional block M1. The peak detection module dynamically detects a peak voltage of the refreshed DIM signal and passes the detected peak voltage through VFThe generator module subtracts the difference Δ V as the predetermined threshold level voltage V for the next cycleF. The reference level VCONT needs to be iteratively added and subtracted in preparation for the next week of control. When the TRIAC is conducted, if the instantaneous voltage of the mains supply is lower than the predetermined valve level voltage VFBut higher than the electrolytic capacitor Cd valley voltage VCd_VALThe charging current of the electrolytic capacitor Cd can still be quickly established; reference level VCONT requires iterationThe preparation for the next cycle of control is added, so that the reference level VCONT of the output voltage of the rectifier bridge before the thyristor dimmer TRIAC in the next cycle is adjusted in an iterative way, and the instant voltage of the mains supply is greater than or close to the equivalent preset valve level voltage V when the thyristor dimmer TRIAC in the next cycle is conductedFI.e. slightly greater than the electrolytic capacitor valley voltage VCd_VAL. Therefore, the electrolytic capacitor can be charged by mains supply through the silicon controlled dimmer in each half cycle. At the time of the conduction of the silicon controlled dimmer TRIAC, the DIM signal corresponding to the instantaneous voltage of the mains supply and the predetermined valve level voltage VFComparing if DIM signal of instantaneous voltage of mains supply is greater than predetermined threshold level voltage VFReducing the output voltage VCONT; this adds and subtracts the regulated output voltage VCONT via the accumulator 1+ DAC1 module as a decision reference level for the rectifier bridge output voltage to start regulating before the TRIAC turns on.
Fig. 2 shows the area of the volt-second product generated at the control time of the reference level VCONT for the area of the volt-second product required for the conduction of different TRIAC dimmers, so as to ensure that the corresponding mains instantaneous voltages are TRIAC TURN _ ON when the TRIAC dimmer is turned ON.
The peak detection module within block M1 outputs a peak voltage VPEAKSubtracting Δ V to obtain a valve level VFAs shown in fig. 2. When the feedback signal DIM is greater than or equal to the reference level VCONT1, or VCONT2, or VCONT3, or VCONT4, respectively, corresponding to different time constants of the TRIAC, the output voltage of the rectifier bridge corresponding to the waveform V is ensured by the output voltage regulating loop of the rectifier bridge before the TRIAC is turned onLEVELThen the TRIAC of the TRIAC dimmer is turned ON, and the corresponding mains instantaneous voltage is TRIAC TURN _ ON. It is obvious that the larger the volt-second time constant set for the TRIAC dimmer, the lower the corresponding reference level VCONT, VLEVELThe longer the duration; and vice versa. Each time the silicon controlled dimmer TRIAC is conducted, the corresponding mains supply instantaneous voltage corresponds to the corresponding valve level VFComparing, if comparing the valve level VFHigh, causes the reference level VCONT to iteratively decrease;if ratio valve level VFLow, the reference level VCONT is caused to increase iteratively;
in summary, the iterative adjustment of the reference voltage VCONT is to ensure that the corresponding mains instantaneous voltage is TRIAC TURN _ ON when the TRIAC is turned ON. Voltage waveform VLEVELCan have various waveforms, and the key is the mains input instantaneous voltage Vin (t) -VLEVELAnd starts integration until the voltage-second product reaches the voltage-second product corresponding to the conduction of the TRIAC, that is, the output voltage of the rectifier bridge and the voltage waveform V in popular languageLEVELThe area over which the voltage difference between them increases with time is the corresponding volt-second product. When the area is the voltage-second product corresponding to the voltage-second product and reaches the voltage-second product corresponding to the conduction of the silicon controlled dimmer, the silicon controlled dimmer TRIAC is conducted. At the time of the TRIAC conduction, the valve level V is compared with the corresponding value when the instantaneous voltage is input according to the commercial powerFIf the voltage is high or low, the output control of the comparator 1 module iteratively adjusts the reference level VCONT, so that the instantaneous voltage of the mains supply input at the moment of the conduction of the thyristor dimmer TRIAC is at the corresponding valve level VFNearby.
In order to complete the second task, the function block M1, the external power device Q1, the electrolytic capacitor Cd, the detection resistor R2, the isolation diode D1, the rectifier bridge, the silicon controlled dimmer TRIAC and the mains supply form an electrolytic capacitor charging control loop, and a reference level V set inside the function block M1CHA_REFParticipate in completing this task. The magnitude of the charging current is set by VCHA_REFAnd a detection resistor R2, wherein the sum of the charging current and the LED output current is larger than the holding current of the silicon controlled dimmer TRIAC; the pulse width of the charging current is determined by the difference between the output voltage of the rectifier bridge and the voltage on the electrolytic capacitor and the conduction angle of the silicon controlled rectifier dimmer; the value of the valley voltage of the electrolytic capacitor Cd is typically chosen so that the charging current pulse width at full power input is approximately one sixth of the mains cycle, taking efficiency and power considerations into account. Considering the dimming variation range of the output LED current, it is common to design the charging current amplitude of the electrolytic capacitor Cd to be larger than the holding current of the thyristor dimmer.
To accomplish task three, of function block M1And the LED current control loop is output, and the conduction angle of the corresponding silicon controlled rectifier dimmer TRIAC is completed. The output LED current control loop of block M1 generates a corresponding change in LED output current based on the change in the electrolytic capacitor charging current pulse width corresponding to the conduction angle of the TRIAC dimmer. Because the voltage on the electrolytic capacitor of the energy storage element is always controlled to be larger than the working voltage V of the LEDLEDThis results in an output LED current ILEDIs a direct current without strobing. Output LED current ILEDThe control loop is based on the valley voltage V of the electrolytic capacitorCd_VALSpecific LED load voltage VLEDHow much higher to iteratively adjust the accumulator 2+ DAC2 module output reference voltage LED-REF. Due to the valley voltage V of the electrolytic capacitorCd_VALCan control the voltage V larger than the LED loadLEDNamely, the power can be continuously supplied, and the LED current can be possible without stroboflash. The voltage on the LED current source is the voltage on the electrolytic capacitor Cd minus the LED load voltage VLED. The voltage on the LED current source provides the valley voltage V of the electrolytic capacitor CdCd_VALAnd LED load voltage VLEDDifference voltage VDiffThe valley voltage V of the corresponding electrolytic capacitor Cd on the LED current source can be adjustedCd_VALAnd LED load voltage VLEDDifference voltage VDiffAnd a predetermined value VValCompared with iterative adjustment, the accumulator 2+ DAC2 module is adjusted to output a reference voltage LED-REF corresponding to the reference level of the LED output current, i.e. the minimum value V of the voltage across the LED current source at each time the electrolytic capacitor Cd is chargedDiffAnd a predetermined value VValA comparison is made to determine a subsequent LED current reference level LED-REF. When the minimum value V of the voltage on the LED current sourceDiffRatio predetermined value VValWhen the voltage is low, the output reference voltage LED-REF of the accumulator 2+ DAC2 module is reduced in an iterative mode; when the minimum value V of the voltage across the LED current sourceDiffRatio predetermined value VValWhen the voltage is high, the output reference voltage LED-REF of the accumulator 2+ DAC2 module is increased in an iterative mode; this makes it possible to minimize the voltage across the LED current sourceDiffAlways booking a value VValAnd nearby, the LED current is ensured to have no stroboflash, and the efficiency as high as possible is achieved.
Example 2 use of a Power PNP transistor as an external Power device Q1 (FIG. 1.b)
The positive ends of the output voltages of the rectifier bridges are respectively connected with the following components: an external ground voltage division network formed by connecting resistors RU and RD in series, an HV _ I pin of a functional block M1, an HV _ C pin of a functional block M1 and an emitter (shown in figure 1.b) of an external power device Q1 after an Rc resistor; the collector of the external power device Q1 is connected with the anode of an isolation diode D1;
the base of the external power device Q1 is connected with the HV _ C pin and the Rc resistor of the functional block M1;
the remainder is equivalent to the above-mentioned "one".
That is, in embodiment 2, compared with embodiment 1, Q1 is changed from the N MOSFET of embodiment 1 to be assumed by a PNP transistor. The driving characteristic of the PNP transistor corresponds to a corresponding change in Rc value of the driving circuit, and the control principle is similar to that of fig. 3.
Finally, it is also noted that the above-mentioned lists merely illustrate a few specific embodiments of the invention. It is obvious that the invention is not limited to the above embodiments, but that many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.
Claims (7)
1. Compatible silicon controlled rectifier dimmer does not have stroboscopic LED drive circuit, characterized by: the LED power supply comprises a rectifier bridge, a functional block M1, an external power device Q1, an external ground voltage division network formed by connecting resistors RU and RD in series, an isolating diode D1, an electrolytic capacitor Cd, a charging current detection resistor R2, an LED load string and an LED output current detection resistor R3;
the mains supply is supplied to a rectifier bridge through a silicon controlled dimmer TRIAC, the negative end of the output voltage of the rectifier bridge is grounded, and the positive end of the output voltage of the rectifier bridge is respectively connected with the following components: an external ground voltage division network formed by connecting resistors RU and RD in series, an HV _ I pin of a functional block M1, an HV _ C pin of a functional block M1 and an electrode I of an external power device Q1 after an Rc resistor; the pole III of the external power device Q1 is connected with the HV _ C pin and the Rc resistor of the functional block M1; the pole II of the external power device Q1 is connected with the anode of an isolation diode D1; isolation diodeThe negative electrode of the D1 is connected with the positive end LED + of the LED load string and the positive end of the electrolytic capacitor Cd; the negative end of the electrolytic capacitor Cd is grounded through a charging current detection resistor R2; a connecting line of the electrolytic capacitor Cd and the charging current detection resistor R2 is connected with a CSCAP pin of the functional block M1; the LED load string negative terminal LED-is connected with the LED-pin of the functional block M1, and the Cs pin of the functional block M1 is grounded through an LED output current detection resistor R3; the CSPULL pin of the functional block M1 and the external resistor R1 form an internal voltage-controlled current source IVCONT(ii) a A DIM pin of the functional block M1 is connected with a connection line of the resistors RU and RD; the GND pin of the functional block M1 is connected with the output voltage negative terminal of the rectifier bridge and the ground; information on the current flowing through the charging current detection resistor R2 and the LED output current detection resistor R3 is fed back to the function block M1 in the form of voltage.
2. The flicker-free LED driving circuit of a compatible silicon controlled dimmer as set forth in claim 1, wherein: the external power device Q1 is a power MOS tube;
the positive ends of the output voltages of the rectifier bridges are respectively connected with the following components: an external ground voltage division network formed by connecting resistors RU and RD in series, an HV _ I pin of a functional block M1, an HV _ C pin of a functional block M1 and a drain electrode of an external power device Q1 after an Rc resistor;
the source of the external power device Q1 is connected with the anode of an isolation diode D1;
the gate of external power device Q1 is connected to pin HV _ C and Rc resistor of functional block M1.
3. The flicker-free LED driving circuit of a compatible silicon controlled dimmer as set forth in claim 1, wherein: the external power device Q1 is a power PNP triode;
the positive ends of the output voltages of the rectifier bridges are respectively connected with the following components: an external ground voltage division network formed by connecting resistors RU and RD in series, an HV _ I pin of a functional block M1, an HV _ C pin of a functional block M1 and an emitter of an external power device Q1 after an Rc resistor;
the collector of the external power device Q1 is connected with the anode of an isolation diode D1;
the base of the external power device Q1 is connected to HV _ C pin and Rc resistor of the functional block M1.
4. The LED driving circuit compatible with the SCR dimmer and free of stroboscopic effect as claimed in any one of claims 1 to 3, wherein:
the function block M1 is provided with the following 8 pins respectively: HV _ C pin, HV _ I pin, DIM pin, CSPULL pin, GND pin, Cs pin, CSCAP pin, LED-pin;
the function block M1 comprises a peak value detection module, a VF generator module, a comparator 1 module and an accumulator 1+ DAC1 module which are connected in sequence by signals; the peak value detection module outputs Vpeak to the VF generator module, the VF generator module outputs VF to the comparator 1 module, and the comparator 1 module outputs corresponding addition and subtraction logic signals to the accumulator 1+ DAC1 module;
the DIM pin is respectively connected with the peak value detection module, the comparator 1 module, the comparator 2 module and the error amplifier 1 module;
the accumulator 1+ DAC1 module outputs VCONT to the comparator 2 module, the comparator 2 module outputs a zero crossing logic signal and a clock logic signal corresponding to the on-jump of the SCR dimmer TRIAC according to the input DIM and VCONT signals, and the clock logic signal is simultaneously transmitted to the accumulator 1+ DAC1 module, the accumulator 2+ DAC2 module, the valley comparison module, the error amplifier 2 module and the error amplifier 1 module;
the input of the error amplifier 1 module is DIM, Vlevel analog signals, zero-crossing logic signals and clock logic signals; the clock logic signal and the zero-crossing logic signal respectively control the error amplifier 1 module to start working and reset; according to DIM and Vlevel analog signals, the error amplifier 1 module outputs control signals to the voltage-controlled current source I1 and the voltage-controlled current source I2 respectively; the positive end of the voltage-controlled current source I1 is connected with the normally-open end of the switch, and the negative end of the voltage-controlled current source I1 is connected with the CSPULL pin; the normally closed end of the switch is connected with an HV _ I pin, the HV _ I pin is connected with the positive end of a voltage-controlled current source I2, and the negative end of the voltage-controlled current source I2 is grounded; the combination of the voltage controlled current source I1 and the voltage controlled current source I2 forms an internal voltage controlled current source IVCONT；
The two inputs of the valley value comparison module are respectively the voltage and the preset value V on the LED output current source fed back by the LED-pinVal(ii) a The valley value comparison module is controlled by a clock logic signal output by the comparator 2 module; the valley value comparison module outputs corresponding addition and subtraction logic signals to the accumulator 2+ DAC2 module, and the accumulator 2+ DAC2 module outputs LED-REF to the error amplifier 3 module;
the positive end of the voltage-controlled current source I3 is connected with the LED-pin, and the negative end of the voltage-controlled current source I3 is connected with the Cs pin; the control end of the voltage-controlled current source I3 is connected with the output of the error amplifier 3 module; the error amplifier 3 module controls the control end of the voltage-controlled current source I3 according to the input LED-REF signal and the feedback signal output provided by the Cs pin, so that the output current of the voltage-controlled current source I3 is equal to LED-REF/R3;
the positive end of the voltage-controlled current source I4 is connected with the HV _ C pin, and the negative end of the voltage-controlled current source I4 is connected to the ground; the control end of the voltage-controlled current source I4 is controlled by the output of the error amplifier 2 module; the error amplifier 2 module is based on the input fixed analog quantity VCHA-REFThe output current of the voltage-controlled current source I4 is controlled by a feedback signal provided by a CSCAP pin and a clock logic signal output by the comparator 2 module, so that the output current controls the input current of an external power device Q1 through an external resistor Rc, and the charging current of an electrolytic capacitor Cd is equal to VCHA-REF/R2。
5. The LED driving circuit compatible with the SCR dimmer and free of stroboscopic effect as claimed in any one of claims 1 to 4, wherein:
the function block M1 finds a proper reference voltage VCONT according to a voltage division network feedback voltage signal DIM formed by RU and RD to ensure that the instantaneous voltage of the mains supply is greater than the valley voltage of the electrolytic capacitor Cd when the silicon controlled dimmer TRIAC is switched on;
by means of the accumulator 1+ DAC1 module generating the reference voltage VCONT by the peak detection module in the functional block M1, the comparator 1 module, the comparator 2 module, the internal voltage controlled current source IVCONTAnd the output voltage of the rectifier bridge form a regulating loop.
6. The LED driving circuit compatible with the SCR dimmer and free of stroboscopic effect as claimed in any one of claims 1 to 4, wherein:
the function block M1, an external power device Q1, an electrolytic capacitor Cd, a detection resistor R2, an isolation diode D1, a rectifier bridge, a silicon controlled dimmer TRIAC and a mains supply form an electrolytic capacitor Cd charging control loop; and controlling the amplitude of the charging current of the electrolytic capacitor Cd to be larger than the holding current of the silicon controlled dimmer TRIAC.
7. The LED driving circuit compatible with the SCR dimmer and free of stroboscopic effect as claimed in any one of claims 1 to 4, wherein: the function block M1, the LED load, the electrolytic capacitor Cd and the LED output current detection resistor R3 form an output LED current control loop, and the output LED current of the output LED current control loop is the valley voltage V of the electrolytic capacitor CdCd_VALAnd (5) controlling.
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