CN101984732A - Control method of light emitting diode (LED) constant current power supply and LED constant current power supply circuit - Google Patents
Control method of light emitting diode (LED) constant current power supply and LED constant current power supply circuit Download PDFInfo
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Abstract
The invention relates to a control method of a light emitting diode (LED) constant current power supply and an LED constant current power supply circuit. In the invention, the control method of the LED constant current power supply is as follows: extracting an input voltage signal, an input current signal and a feedback voltage signal, then inputting the signals to a control circuit; converting the acquired signals into digital signals by the control circuit, adding a frequency jitter signal; carrying out logical operation to obtain a pulse signal for controlling a switch to work; and isolating the high-frequency alternative current by the high-frequency transformer so as to perform constant current driving on the LED. In the invention, the LED constant current power supply comprises a control circuit, a power supply unit, an input voltage detection unit, an output frequency jitter control unit, an output voltage detection unit, a primary current detection unit, a switch S1, a high frequency transformer and an output filter unit. The circuit of the invention can automatically adapt to the change of load LEDs and eliminate the impact of the circuit parameter change on working condition, thereby ensuring long-term stable work of the circuit.
Description
Technical field
The present invention relates to a kind of control method and LED constant-current power supply circuit of LED constant-current supply.
Background technology
Along with of more and more widely the application of LED lamp, more and more urgent for the requirement of the driving power that can satisfy the requirement of LED lamp high performance and long service life at lighting field.According to the technical standard of LED lighting apparatus, the LED driving power will satisfy safety standard, the Electro Magnetic Compatibility standard.And want small size, the high temperature environment long time continuous working.The method for designing of traditional Switching Power Supply is difficult to satisfy its requirement.Add the electric property that LED itself is special, the consistency problem of traditional power supply method for designing when producing in enormous quantities is more outstanding.
Present reasonable drive scheme has National Semiconductor (National Semiconductor) to release a LM3445, it is the special-purpose control integrated circuit of a LED, its application circuit as shown in Figure 1, the inside schematic diagram of LM3445 is as shown in Figure 2.
The characteristics of this circuit are: be a special constant-current driving control circuit at the LED characteristic, adopt adjustable fixedly shutoff mode, simplify the sampling feedback compensation loop of conventional switch power supply complexity, can satisfy constant-current driving and high temperature environment reliability during operation.
Its shortcoming is: 1, adopt the outside passive device power factor compensation circuit of frame of broken lines 1, generally can only reach 0.75 power factor (PF) during volume production; 2, adopt the inductance work wave sampling of frame of broken lines 2, disturb greatlyyer, the consistency of volume production affects adversely; 3, adopt the mode of non-isolation, when satisfying safety standard, will spend more cost.
Switching Power Supply frequency jitter technology is meant that the operating frequency of Switching Power Supply is not to immobilize, but periodically changes the method that reduces electromagnetic interference.Its principle is to disperse the distribution of the each harmonic component of electromagnetic noise by the variation of operating frequency, effectively reduces the peak value of each time noise.
The TOPSwitch series of Power integrations company is to adopt the typical case of this technology to use.The TOPSwitch family chip be a kind of inside integrated the power chip of pwm control circuit and MOSFET, operating frequency is 132kHz, and periodically is that the center changes 4kHz up and down with 132kHz.In the 4ms cycle (frequency is 250Hz), finish once from the frequency jitter between the 128kHz to 136kHz.Its fundamental diagram as shown in Figure 3.Its weak point pattern that has been internal fixation, relatively poor to the adaptability of different practical applications.And with fixing frequency change cycling, the distribution discreteness of each harmonic is big not enough, and its ability that reduces electromagnetic interference also has the space that promotes.
Summary of the invention
First purpose of the present invention is the problems referred to above at existing LED control method existence, provide a kind of and can adapt to the variation of load LED automatically and eliminate the influence of circuit parameter variations, guarantee the control method of the LED constant-current supply of circuit long-term stable operation operating state.
Second purpose of the present invention is the problems referred to above at existing switching circuit existence, provide a kind of and can adapt to the variation of load LED automatically and eliminate the influence of circuit parameter variations, guarantee the LED constant-current power supply circuit of circuit long-term stable operation operating state.
The control method of LED constant-current supply of the present invention is as follows: extract input voltage signal, input current signal, feedback voltage signal input control circuit, control circuit is the conversion of signals that obtains digital signal and adds the pulse signal of frequency jitter signal through the controlled switching tube work of logical operation, the high-frequency alternating current of gained is isolated through high frequency transformer, and LED is carried out constant-current driving; Described frequency jitter signal adopts when not required, and the frequency jitter pattern of the Preset Time of clock signal obtains.
As preferred version, the frequency jitter pattern of described Preset Time is to change the time of each work period in the additional little different time period of each turn-off time of switching tube.The voltage of described little different time period by the change that control circuit provides produces capacitor charge and discharge by a resistance, perhaps electric capacity is charged by the resistance of fixing voltage by change, or set different electric capacity charging voltage values and obtain the different time periods, this time is freely set, control circuit detects this time and is used to set the time span difference of each work period of control circuit, the result is that the time span of each work period has fine distinction, thereby has realized the shake of operating frequency.
As preferred version, described control circuit has the judgement of self adaptation turn-off time, and the level of monitoring output voltage obtains the turn-off time that the time period participation that is higher than predetermined level forms the power controlling switching tube.
As preferred version, the present invention adopts little current start mode, and little electric current provides electric current to control loop during startup, supports that switching tube carries out startup work, provides power supply by the auxiliary power supply loop subsequently.
LED constant-current power supply circuit of the present invention comprises:
A control circuit is used for input voltage signal, input current signal, the feedback voltage signal of input are converted to digital signal and add the pulse signal of frequency jitter signal through the controlled switching tube work of logical operation;
A power supply unit is used for to described control circuit power supply;
An input voltage detecting unit is used to detect input voltage and the input voltage signal input control circuit that detects is participated in output current control and power factor (PF) control;
An output frequency shake control unit, the frequency jitter pattern of employing Preset Time is used for changing the time of each work period in the additional little different time period of each turn-off time of switching tube;
An output voltage waveforms detecting unit is used to detect output voltage waveforms and feedback voltage signal is entered control of control circuit participation output current and power factor (PF) control;
A primary current detecting unit is used to detect primary current and the detection signal input control circuit is participated in output current control and power factor (PF) control.
A switching tube S1 provides the primary current path of high frequency transformer L, and the high-low level that drives this switching tube is provided by control circuit;
A high frequency transformer L, its secondary provides constant-current supply for the output filter unit;
An output filter unit is for load LED lamp provides direct current.
As preferred version, described control circuit has the judgement of self adaptation turn-off time, and the level of control circuit monitoring output voltage obtains the turn-off time that the time period participation that is higher than predetermined level forms the power controlling switching tube.
As preferred version, described control circuit comprises a start-up circuit, an arithmetic logic unit, an output driver element, a voltage cell, an input voltage detecting unit, a voltage waveform generating unit, 5 comparator unit and an internal reference voltage cell; Described voltage cell comprises voltage source 1, and described voltage waveform generating unit comprises voltage source 2, comparator 5, discharge tube K1; The Vin port of described control circuit connects start unit, output driver element and auxiliary power supply port Vcc by a diode D, for inside provides starting resistor; The Vt port of described control circuit connects the input voltage detecting unit; The Vdd port of described control circuit is the output of voltage source 1, for external circuit provides a burning voltage, belongs to standby functions; The Vf of described control circuit is the output of voltage source 2, exports for the outside provides the voltage of a variation, participates in forming the frequency jittering function of Preset Time; The Fs port of described control circuit is connected with comparator 5 and discharge tube K1, participates in forming the frequency jittering function of Preset Time; The Vcc port of described control circuit is connected with diode D, start unit, output driver element, for inside provides operating voltage; The Vout port of described control circuit is connected with the output driver element, and the drive level of external switch pipe S1 is provided; The GND port of described control circuit is the ground level port of inside; The Is port of described control circuit is connected with comparator 1, detects the primary current signal of external circuit; The Tc port of described control circuit is connected with comparator 2,3,4, detects the output feedback voltage of external circuit; The internal reference voltage cell of described control circuit is for inner each comparator provides reference voltage; The arithmetic logic unit of described control circuit and comparator 1,2,3,4,5 and input voltage detecting unit, output driver element, start unit are connected, input signal handled obtaining an impulse level, amplify the switching tube S1 of rear drive outside through the output driver element.
As preferred version, described output frequency shake control unit is composed in series by a resistance R _ f and capacitor C f, the Vf port of the other end connection control circuit of resistance R _ f, the Fs end port of the other end connection control circuit of capacitor C f.
As preferred version, described power supply unit comprises a little current start resistance R 1 and an auxiliary power supply loop, and described little current start resistance R 1 is connected between the Vin port of external power supply and control circuit; Described auxiliary power supply loop is made of diode D1, resistance R 2, capacitor C 1, one end of resistance R 2 connects the Vcc port of control circuit, the other end is connected with capacitor C 1 with the negative pole of diode D1, another utmost point ground connection of capacitor C 1, and the positive pole of diode D1 connects the former limit of high frequency transformer; Little electric current by little current start resistance R 1 when the LED constant-current power supply circuit starts provides electric current to control loop, supports switching tube S1 to carry out startup work, subsequently by the auxiliary power supply loop power supply, and the function of supplying power of closing control circuit Vin port; Described input voltage detecting unit is made up of resistance R 3 and resistance R 4, a termination external power supply of resistance R 3, the Vt port of other end connecting resistance R4 and control circuit, the other end ground connection of resistance R 4; Described output voltage waveforms detecting unit is made up of resistance R 5, resistance R 6 and diode D2, one end of resistance R 5 is connected with the negative pole of diode D2, the other end is connected with resistance R 6 with the Tc port of control circuit, the other end ground connection of resistance R 6, the positive pole of diode D2 connects the former limit of high frequency transformer; Described primary current detecting unit is made up of resistance R s, and the one end connects the Tc port of control circuit, other end ground connection; One end of the former limit N1 winding of described high frequency transformer L connects the D end of switching tube S1, and the other end is connected with external power supply, and the secondary N3 winding of high frequency transformer L provides constant-current supply to the output filter unit; Described output filter unit is made up of diode D3 and capacitor C out, the positive pole of diode D3 connects an end of N3 winding, negative pole connects the end of capacitor C out and the positive pole of load LED, the positive pole of the termination load LED of capacitor C out, one end of another termination N3 winding, the output filter unit provides direct current to load LED lamp.
Operation principle of the present invention is: the present invention is a kind of LED constant-current driving method that adopts high frequency transformer to isolate with the work of Switching Power Supply mode.Main points of the present invention are: (1) adopts the frequency jitter pattern of Preset Time; (2) to the proportion sample of output voltage waveforms.Above characteristics make circuit of the present invention can adapt to the variation of load LED automatically and eliminate the influence of circuit parameter variations to operating state, guarantee the circuit long-term stable operation.
Technique effect of the present invention is specific as follows:
1, control circuit adopts digital working method.Promptly all sampling signals of telecommunication all are converted to the high-low level signal.Its advantage is:
1) simplified control circuit, can be with than the specific function of the more low-cost realization of analog circuit.
2) reliability of intensifier circuit, anti-interference.Guaranteeing under complex electromagnetic environment and the hot environment that circuit is in that ability substantially exceeds analog circuit under the normal operating conditions.
2, adopt the operation principle of self adaptation turn-off time.Electrical quantity that can extraordinary compatible different LED lamp changes and the back LED electrical property that works long hours changes, and guarantees the reliability that the consistency produced in batches and complete machine work long hours.
3, adopt the input voltage sampling, the sampling of transformer primary current, the three resamplings control of taking a sample of transformer original edge voltage.Realize high power factor (greater than 0.9) with least cost.The electrical property and the constant current accuracy of whole power supply are guaranteed, and the consistency of batch process is guaranteed.Can be more convenient and least cost ground realize isolation drive, satisfy the requirement of safety standard and the safe handling of protection LED luminous element easily.
4, adopt the frequency jitter technology.Adopt the frequency jitter pattern of Preset Time, change the time of each work period in the additional little different time period of the turn-off time of each switching tube, the cycle of frequency change and the cycle of circuit working do not have correlation fully, the mode in the cycle that the discreteness ratio employing fixed frequency that makes each harmonic distribute changes is bigger, more effectively reduce the electromagnetic radiation of circuit, and can freely set the electrical property that the additional time period cooperates filtering link circuit better, satisfy the Electro Magnetic Compatibility index with minimum cost.
5, adopt little current start mode.Effective to improving power-efficient and reducing the power supply cost.
Description of drawings
Fig. 1 is the application circuit of the special-purpose control integrated circuit LM3445 of LED.
Fig. 2 is the inside schematic diagram of the special-purpose control integrated circuit LM3445 of LED.
Fig. 3 is the fundamental diagram of TOPSwitch family chip.
Fig. 4 is the circuit theory diagrams of the embodiment of the invention.
Fig. 5 is the inside theory diagram of control circuit in the embodiment of the invention.
Fig. 6 is the oscillogram of waveform when operate as normal that self adaptation drives the detected Vs ' point of output voltage waveforms detecting unit of operation principle in the embodiment of the invention.
Embodiment
Referring to Fig. 4, present embodiment is a LED constant-current power supply circuit that has adopted control method of the present invention, and it comprises a control circuit, a power supply unit, an input voltage detecting unit, an output frequency shake control unit, an output voltage waveforms detecting unit, a primary current detecting unit, switching tube S1, a high frequency transformer L.
Referring to Fig. 4 and Fig. 5, described control circuit is used for input voltage signal, input current signal, the feedback voltage signal of input are converted to digital signal and add the pulse signal of the frequency jitter signal of Preset Time through the controlled switching tube work of logical operation.
Referring to Fig. 5, the control circuit in the present embodiment comprises a start-up circuit, an arithmetic logic unit, an output driver element, a voltage cell, an input voltage detecting unit, a voltage waveform generating unit, 5 comparator unit and an internal reference voltage cell; Described voltage cell comprises voltage source 1, and described voltage waveform generating unit comprises voltage source 2, comparator 5, discharge tube K1.
The Vin port of described control circuit connects start unit, output driver element and auxiliary power supply port Vcc by a diode D, for inside provides starting resistor;
The Vt port of described control circuit connects the input voltage detecting unit;
The Vdd port of described control circuit is the output of voltage source 1, for external circuit provides a burning voltage, belongs to standby functions;
The Vf of described control circuit is the output of voltage source 2, exports for the outside provides the voltage of a variation, participates in forming the frequency jittering function of Preset Time;
The Fs port of described control circuit is connected with comparator 5 and discharge tube K1, participates in forming the frequency jittering function of Preset Time;
The Vcc port of described control circuit is connected with diode D, start unit, output driver element, for inside provides operating voltage;
The Vout port of described control circuit is connected with the output driver element, and the drive level of external switch pipe S1 is provided;
The GND port of described control circuit is the ground level port of inside;
The Is port of described control circuit is connected with comparator 1, detects the primary current signal of external circuit;
The Tc port of described control circuit is connected with comparator 2,3,4, detects the output feedback voltage of external circuit;
The internal reference voltage cell of described control circuit is for inner each comparator provides reference voltage;
The arithmetic logic unit of described control circuit and comparator 1,2,3,4,5 and input voltage detecting unit, output driver element, start unit are connected, input signal handled obtaining an impulse level, amplify the switching tube S1 of rear drive outside through the output driver element.
Referring to Fig. 4, Fig. 5, described power supply unit is used for to described control circuit power supply.Power supply unit in the present embodiment comprises a little current start resistance R 1 and an auxiliary power supply loop, described little current start resistance R 1 is connected between the Vin port of external power supply and control circuit, and external AC power supply is through connecting little current start resistance R 1 behind the rectifier bridge; Described auxiliary power supply loop is made of diode D1, resistance R 2, capacitor C 1, one end of resistance R 2 connects the Vcc port of control circuit, the other end is connected with capacitor C 1 with the negative pole of diode D1, another utmost point ground connection of capacitor C 1, and the positive pole of diode D1 connects the former limit of high frequency transformer.Little electric current by little current start resistance R 1 when the LED constant-current power supply circuit starts provides electric current to control loop, support switching tube S1 to carry out the work of start-up period, subsequently by the auxiliary power supply loop power supply, the function of supplying power of the inside start unit closing control circuit Vin port of control circuit.
Referring to Fig. 4, described input voltage detecting unit is used to detect input voltage and the detection signal input control circuit is participated in output current control and power factor (PF) control.Input voltage detecting unit in the present embodiment is shown in the frame of broken lines 1 among Fig. 4, is made of a termination external power supply of resistance R 3, the Vt port of other end connecting resistance R4 and control circuit, the other end ground connection of resistance R 4 resistance R 3 and resistance R 4.
Referring to Fig. 4, Fig. 5, described output frequency shake control unit adopts the frequency jitter pattern of Preset Time, is used for changing the time of each work period in the additional little different time period of each turn-off time of switching tube.Output frequency shake control unit be shown in the frame of broken lines 2 among Fig. 4 in the present embodiment, is to be composed in series by a resistance R _ f and capacitor C f, the Vf port of the other end connection control circuit of resistance R _ f, and the Fs of the other end connection control circuit of capacitor C f holds port.Its operation principle is:
The Vf port of control circuit provides the drive level of a variation, can be sine and cosine voltage waveform, triangular wave, sawtooth waveforms etc. or the irregular voltage waveform of amplitude.To capacitor C f charging, because the fluctuation of Vf voltage, also there is difference in the charging interval that capacitor C f reaches identical voltage to the voltage of Vf by resistance R _ f.The Fs end of control circuit detects this time and is used to set the time difference of each work period of control circuit, and the result who obtains in this way has fine distinction the time of each work period, thereby has realized the shake of operating frequency.Its advantage is simple and reliable for structure, can regulate the frequency and the distribution of shake, for cooperating different Electro Magnetic Compatibility filter circuits to provide convenience in different application scenarios, obtains the more optimal design of satisfying the Electro Magnetic Compatibility standard.
Referring to Fig. 4, Fig. 5, the Tc port that described output voltage waveforms detecting unit is used to detect output voltage waveforms and feedback voltage signal is entered control circuit, comparator by Tc port inside is converted to digital signal with the voltage signal that obtains, and is used to form the turn-off time control of control switch pipe S1.Output voltage waveforms detecting unit in the present embodiment is shown in the frame of broken lines 2 among Fig. 4, form by resistance R 5, resistance R 6 and diode D2, one end of resistance R 5 is connected with the negative pole of diode D2, the other end is connected with resistance R 6 with the Tc port of control circuit, the other end ground connection of resistance R 6, the positive pole of diode D2 connects the former limit N2 winding of high frequency transformer.
Detected waveform Vs ' of output voltage waveforms detecting unit and Vs waveform are proportional.Waveform during operate as normal as shown in Figure 6.
Vs ' waveform enters the Tc end of control circuit.Tc end internal logic is handled the comparator 2 with the judgement of self adaptation turn-off time, the comparator 3 that open-circuit-protection is judged, the comparator 4 of short-circuit protection judgement and partial resonance opening time arbitration functions.
Realize that comparative level of self adaptation turn-off time minimum needs Vset1 of judgement is a comparator 2.
Its operation principle is that Tc port inside has three comparators to set three reference level Vset0, Vset1, Vset2 respectively.Vs voltage is in off state at the time period t 1 maintained switch pipe S1 that is higher than Vset1 during operate as normal between Vset1, Vset2.Because the special electrical property of LED, different LED can show different t1, and promptly t1 is only relevant with LED.The key of adaptive LED driving that Here it is.Its advantage be no matter be in producing in batches the electrical property of LED distribute or the course of work in the variation of LED electrical property, and the variation of the control circuit internal circuit parameter that causes of a variety of causes (for example variation such as ambient temperature), this circuit all works in the preset working state automatically, can be because of entering unexpected working point, cause drives fail or decreased performance, the lost of life.
The t2 time period is to be determined by the additional time period of the frequency jitter unit of frame of broken lines 2.
Open-circuit-protection, when Vs ' was higher than Vset2, control circuit entered guard mode.
Short-circuit protection is worked as the state that Vset0 does not appear being higher than in Vs ', and control circuit enters the open-circuit-protection state.
Referring to Fig. 4, Fig. 6, described primary current detecting unit is used to detect primary current and with detection signal input control circuit Is port, and the comparator 1 in the Is port is converted to digital signal with detected voltage signal and by the service time length T on of this digital signal determine switch pipe S1.Primary current detecting unit in the present embodiment is made up of resistance R s, and the one end connects the Ts port of control circuit, other end ground connection.
Referring to Fig. 4, the G utmost point of switching tube S1 is connected with the Vout of control circuit end, and the D utmost point of switching tube S1 is connected with the former limit N1 winding of transformer, and the S utmost point of switching tube S1 connects resistance R s.Provide the high-low level of driving switch pipe S1 by this port, the high-frequency alternating current of gained connects the former limit of high frequency transformer.
Referring to Fig. 4, an end of the former limit N1 winding of present embodiment medium-high frequency transformer L connects the D end of switching tube S1, and the other end is connected with external AC power supply through rectifier bridge, and the secondary N3 winding of high frequency transformer L provides constant-current supply to the output filter unit; Described output filter unit is made up of diode D3 and capacitor C out, and the positive pole of diode D3 connects an end of N3 winding, and negative pole connects the end of capacitor C out and the positive pole of load LED, the positive pole of the termination load LED of capacitor C out, an end of another termination N3 winding.The output filter unit provides direct current to load LED lamp.
Claims (9)
1. the control method of a LED constant-current supply, it is characterized in that: extract input voltage signal, input current signal, feedback voltage signal input control circuit, control circuit is the conversion of signals that obtains digital signal and adds the pulse signal of frequency jitter signal through the controlled switching tube work of logical operation, the high-frequency alternating current of gained is isolated through high frequency transformer, and LED is carried out constant-current driving; Described frequency jitter signal adopts when not required, and the frequency jitter pattern of the Preset Time of clock signal obtains.
2. the control method of LED constant-current supply according to claim 1 is characterized in that: the frequency jitter pattern of described Preset Time is to change the time span of each work period in an additional little different time period in each cycle turn-off time of switching tube.
3. the control method of LED constant-current supply according to claim 2, it is characterized in that: the voltage of described little different time period by the change that control circuit provides produces capacitor charge and discharge by a resistance, perhaps electric capacity is charged by the resistance of fixing voltage by change, or set different electric capacity charging voltage values and obtain the different time periods, this time period is freely set, control circuit detects this time period and is used to set the time difference of each work period of control circuit, the result is that the time span of each work period has fine distinction, thereby has realized the shake of operating frequency.
4. according to the control method of claim 1 or 2 or 3 described LED constant-current supplies, it is characterized in that: described control circuit has the judgement of self adaptation turn-off time, the level of monitoring output voltage obtains the turn-off time that the time period participation that is higher than predetermined level forms the power controlling switching tube.
5. LED constant-current power supply circuit is characterized in that comprising:
A control circuit is used for input voltage signal, input current signal, the feedback voltage signal of input are converted to digital signal and add the pulse signal of frequency jitter signal through the controlled switching tube work of logical operation;
A power supply unit is used for to described control circuit power supply;
An input voltage detecting unit is used to detect input voltage and the input voltage signal input control circuit that detects is participated in output current control and power factor (PF) control;
An output frequency shake control unit, the frequency jitter pattern of employing Preset Time is used for changing the time of each work period in the additional little different time period of each turn-off time of switching tube;
An output voltage waveforms detecting unit is used to detect output voltage waveforms and feedback voltage signal is entered control of control circuit participation output current and power factor (PF) control;
A primary current detecting unit is used to detect primary current and the detection signal input control circuit is participated in output current control and power factor (PF) control;
A switching tube (S1) provides the path by the primary current of high frequency transformer L, and the high-low level of driving switch pipe (S1) is provided by control circuit;
A high frequency transformer (L), its secondary provides constant-current supply for the output filter unit;
An output filter unit is for load LED lamp provides direct current.
6. LED constant-current power supply circuit according to claim 5, it is characterized in that: described control circuit has the judgement of self adaptation turn-off time, the level of control circuit monitoring output voltage obtains the turn-off time that the time period participation that is higher than predetermined level forms the power controlling switching tube.
7. according to claim 5 or 6 described LED constant-current power supply circuits, it is characterized in that: described control circuit comprises a start-up circuit, an arithmetic logic unit, an output driver element, a voltage cell, an input voltage detecting unit, a voltage waveform generating unit, 5 comparator unit and an internal reference voltage cell; Described voltage cell comprises voltage source (1), and described voltage waveform generating unit comprises voltage source (2), comparator (5), discharge tube (K1);
The Vin port of described control circuit connects start unit, output driver element and auxiliary power supply port Vcc by a diode (D), for inside provides starting resistor;
The Vt port of described control circuit connects the input voltage detecting unit;
The Vdd port of described control circuit is the output of voltage source (1), for external circuit provides a burning voltage, belongs to standby functions;
The Vf of described control circuit is the output of voltage source (2), exports for the outside provides the voltage of a variation, participates in forming the frequency jittering function of Preset Time;
The Fs port of described control circuit is connected with comparator (5) and discharge tube (K1), participates in forming the frequency jittering function of Preset Time;
The Vcc port of described control circuit is connected with diode (D), start unit, output driver element, for inside provides operating voltage;
The Vout port of described control circuit is connected with the output driver element, and the drive level of external switch pipe (S1) is provided;
The GND port of described control circuit is the ground level port of inside;
The Is port of described control circuit is connected with comparator (1), detects the primary current signal of external circuit;
The Tc port of described control circuit is connected with comparator (2), comparator (3), comparator (4), detects the output feedback voltage of external circuit;
The internal reference voltage cell of described control circuit is for inner each comparator provides reference voltage;
The arithmetic logic unit of described control circuit is connected with comparator (1), comparator (2), comparator (3), comparator (4), comparator (5) and input voltage detecting unit, output driver element, start unit, input signal handled obtaining an impulse level, amplify the switching tube (S1) of rear drive outside through the output driver element.
8. LED constant-current power supply circuit according to claim 7, it is characterized in that: described output frequency shake control unit is composed in series by resistance (Rf) and electric capacity (Cf), the Vf port of the other end connection control circuit of resistance (Rf), the Fs port of the other end connection control circuit of electric capacity (Cf);
9. LED constant-current power supply circuit according to claim 7, it is characterized in that: described power supply unit comprises a little current start resistance (R1) and an auxiliary power supply loop, and described little current start resistance (R1) is connected between the Vin port of external power supply and control circuit; Described auxiliary power supply loop is made of diode (D1), resistance (R2), electric capacity (C1), one end of resistance (R2) connects the Vcc port of control circuit, the other end is connected with electric capacity (C1) with the negative pole of diode (D1), another utmost point ground connection of electric capacity (C1), the positive pole of diode (D1) connect the former limit N2 winding of high frequency transformer; Little electric current by little current start resistance (R1) when the LED constant-current power supply circuit starts provides electric current to control loop, supports switching tube (S1) to carry out startup work, subsequently by the auxiliary power supply loop power supply, and the function of supplying power of closing control circuit Vin port;
Described input voltage detecting unit is made up of resistance (R3) and resistance (R4), a termination external power supply of resistance (R3), the Vt port of other end connecting resistance (R4) and control circuit, the other end ground connection of resistance (R4);
Described output voltage waveforms detecting unit is made up of resistance (R5), resistance (R6) and diode (D2), one end of resistance (R5) is connected with the negative pole of diode (D2), the other end is connected with resistance (R6) with the Tc port of control circuit, the other end ground connection of resistance (R6), the positive pole of diode (D2) connects the former limit of high frequency transformer;
Described primary current detecting unit is made up of resistance (Rs), and the one end connects the Ts port of control circuit and the S end of switching tube (S1), other end ground connection;
One end of the former limit N1 winding of described high frequency transformer L connects the D end of switching tube (S1), and the other end is connected with external power supply, and the secondary N3 winding of high frequency transformer (L) provides constant-current supply to the output filter unit;
Described output filter unit is made up of diode (D3) and electric capacity (Cout), the positive pole of diode (D3) connects an end of N3 winding, negative pole connects an end of electric capacity (Cout) and the positive pole of load LED, the positive pole of a termination load LED of electric capacity (Cout), an end of another termination N3 winding; The output filter unit provides direct current to load LED lamp.
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| CN2010105445126A CN101984732A (en) | 2010-11-15 | 2010-11-15 | Control method of light emitting diode (LED) constant current power supply and LED constant current power supply circuit |
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| CN104682743A (en) * | 2015-02-10 | 2015-06-03 | 厦门台和电子有限公司 | Multi-output power adapter circuit |
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