CN104039051B - Transformer-free light-emitting diode power supply for illumination - Google Patents

Abstract

The invention provides a light-emitting diode power supply for lighting without a transformer, which includes a main circuit, a constant voltage constant current control circuit and a light-emitting diode power interface; The voltage-dividing capacitors are connected in series to divide the voltage and generate a DC output in the filter energy storage capacitor. When the AC power is input for the negative half cycle, each voltage-dividing capacitor sequentially passes through the corresponding isolation diode, the shared first electronic switch and the inductor to supplement the discharge of the filter energy storage capacitor to generate a DC output. The output circuit; the constant voltage and constant current control circuit is a circuit that processes the sampled voltage signal and the sampled current signal and then acts on the main circuit to ensure the stability of the working voltage and current of the light emitting diode. The invention omits the transformer of the common light-emitting diode lighting power supply, thereby reducing the volume, weight and cost of the power supply.

Description

Transformerless LED power supply for lighting

This application is a divisional application of the invention patent application with the application number 201210109725.5, the application date is April 13, 2012, and the invention name is "LED power supply for transformerless lighting".

technical field

The invention relates to a power supply for lighting, in particular to a transformerless DC stabilized power supply for powering light-emitting diodes.

Background technique

At present, the common DC stabilized power supplies that provide power to light-emitting diodes (LEDs for short) for lighting all contain a transformer for step-down, so the volume cannot be made small and heavy, and the transformer is in the DC stabilized power supply. Occupy a large production cost.

Contents of the invention

The purpose of the present invention is to overcome the disadvantages of the conventional DC stabilized power supply with transformers, such as bulky, bulky, and high cost, and provide a DC stabilized power supply without a transformer for powering LEDs for lighting.

The technical solution of the present invention is: a light-emitting diode power supply for lighting without a transformer. The main circuit is provided with an AC input terminal, a DC power supply output terminal, a first control signal input terminal, a second control signal input terminal, and a constant voltage constant current control circuit power supply output terminal; the above constant voltage constant current control circuit is provided with a sampling voltage input terminal terminal, the first control signal output terminal, the second control signal output terminal, the power supply terminal, the sampling current input terminal and the sampling current output terminal; Electrically connected; the first control signal input end of the main circuit is electrically connected to the first control signal output end of the constant voltage and constant current control circuit; the second control signal input end of the main circuit is connected to the second control signal of the constant voltage and constant current control circuit The output terminal is electrically connected; the output terminal of the power supply of the constant voltage and constant current control circuit of the main circuit is electrically connected to the power supply terminal of the constant voltage and constant current control circuit; the sampling current input terminal of the constant voltage and constant current control circuit is electrically connected to the negative pole of the LED power interface J1 ; The sampling current output terminal of the constant voltage and constant current control circuit is grounded; the positive pole of the LED power supply interface is electrically connected to the DC power output terminal of the main circuit; Diodes and voltage-dividing capacitors are connected in series to divide the voltage and generate a DC output at the filter energy storage capacitor Co. When the input AC is in the negative half cycle, each voltage-dividing capacitor passes through the corresponding isolation diode, the shared first electronic switch Q1 and the inductance coil L1 to filter The energy storage capacitor Co supplements the discharge to generate a DC output circuit; the above-mentioned constant voltage and constant current control circuit processes the sampled voltage signal and sampled current signal and feeds back to the above-mentioned main circuit to ensure the output of the main circuit. DC voltage and DC current stable circuit.

The above-mentioned main circuit includes a voltage dividing discharge circuit, a filter energy storage capacitor Co, a first electronic switch Q1), a second electronic switch Q2, a diode Do2, a freewheeling diode Do1 and an inductance coil L1;

There are n levels of voltage-dividing discharge circuits, and the voltage-dividing discharge circuits of all levels are electrically connected in turn; the voltage-dividing discharge circuits of all levels are composed of voltage-dividing capacitors, rectifier diodes and 2 isolation diodes; all levels of voltage-dividing discharge circuits have input terminal, the first common line terminal, the first output terminal, the second output terminal and the ground terminal; the voltage dividing capacitor is an electrolytic capacitor; the two isolation diodes are divided into the first isolation diode and the second isolation diode; the anode of the rectifier diode It is the input terminal; the negative pole of the rectifier diode, the positive pole of the second isolation diode, and the positive pole of the voltage dividing capacitor are collinear to form a common contact, which is the first common line terminal; the negative pole of the voltage dividing capacitor and the first The cathodes of the isolation diodes are electrically connected to form a common contact, which is the first output terminal; the cathode of the second isolation diode is the second output terminal; the anode of the first isolation diode is the ground terminal; wherein, the main circuit The first-stage voltage-dividing discharge circuit is composed of diode D12 as a rectifier diode, electrolytic capacitor C1 as a voltage-dividing capacitor, diode D11 as the first isolation diode, and diode D13 as the second isolation diode; the anode of diode D12 is both The input end of the first stage voltage divider discharge circuit is also the AC input end of the main circuit. The nth stage voltage divider discharge circuit of the main circuit consists of the diode Dn2 as the rectifier diode, the electrolytic capacitor Cn as the voltage divider capacitor, and the first isolation diode The diode Dn1 and the diode Dn3 as the second isolation diode are composed; the anode of the diode Dn2 is the input end of the nth stage voltage divider discharge circuit, and the input end is connected with the upper stage, that is, the n-1th stage voltage divider discharge circuit. The first output terminal is electrically connected; the cathode of the diode Dn2, the anode of the electrolytic capacitor Cn and the anode of the diode Dn3 are collinear to form a common contact, which is the first collinear terminal and is also the constant voltage and constant current control of the main circuit Circuit power output;

The second output ends of the voltage-dividing discharge circuits at all levels are connected to the input end of the first electronic switch Q1; the output end of the first electronic switch Q1, one end of the inductance coil L1 and the negative pole of the freewheeling diode Do1 are in line; the freewheeling diode The positive pole of Do1 is grounded; the other end of the inductance coil L1, the positive pole of the filter energy storage capacitor Co and the negative pole of the diode Do2 are collinear to form a common contact, which is the DC power output end of the main circuit; the filter energy storage capacitor Co The negative pole and the output end of the second electronic switch Q2 are all grounded; the positive pole of the diode Do2 and the input end of the second electronic switch Q2 are all electrically connected to the first output end of the nth stage voltage divider discharge circuit; the control of the first electronic switch Q1 The terminal is the first control signal input terminal of the main circuit; the control terminal of the second electronic switch Q2 is the second control signal input terminal of the main circuit;

The number of stages n of the voltage divider discharge circuit of the main circuit is calculated according to the calculation formula n=(Vac–Vout)/(m × Vout ) , where Vac is the AC voltage input to the anode of the diode D12, and Vout is the filter energy storage capacitor Co The DC voltage output by the positive pole of , and the value range of m is 1 to 6.

The above-mentioned first electronic switch Q1 is an NPN transistor, a PNP transistor, or a common-collector circuit composed of two PNP transistors; when the first electronic switch Q1 is an NPN transistor, the base of the NPN transistor The pole is the control terminal of the first electronic switch Q1, the collector of the NPN transistor is the input terminal of the first electronic switch Q1, and the emitter of the NPN transistor is the output terminal of the first electronic switch Q1; When an electronic switch Q1 is a PNP transistor, the base of the PNP transistor is the control terminal of the first electronic switch Q1, and the emitter of the PNP transistor is the input terminal of the first electronic switch Q1. The collector is the output terminal of the first electronic switch Q1; when the first electronic switch Q1 is a common-collector circuit composed of two PNP transistors, the base of the composite tube circuit is the first electronic switch The control terminal of Q1, the emitter of the composite tube circuit is the input terminal of the first electronic switch Q1, and the collector of the composite tube circuit is the output terminal of the first electronic switch Q1;

The second electronic switch Q2 is an NPN transistor, a PNP transistor or a common-collector circuit composed of two PNP transistors; when the second electronic switch Q2 is an NPN transistor, the NPN transistor The base is the control terminal of the second electronic switch Q2, the collector of the NPN transistor is the input terminal of the second electronic switch Q2, and the emitter of the NPN transistor is the output terminal of the second electronic switch Q2; When the second electronic switch Q2 is a PNP transistor, the base of the PNP transistor is the control terminal of the second electronic switch Q2, and the emitter of the PNP transistor is the input terminal of the second electronic switch Q2. The collector of the triode is the output end of the second electronic switch Q2; when the second electronic switch Q2 is a common collector-common collector circuit composed of two PNP transistors, the base of the composite tube circuit is the second electronic switch. The control terminal of the switch Q2, the emitter of the composite tube circuit is the input terminal of the second electronic switch Q2, and the collector of the composite tube circuit is the output terminal of the second electronic switch Q2.

The above-mentioned voltage stabilizing constant current control circuit comprises dual voltage comparator U1, triode Q3, diode D1, diode D2, resistance R1, resistance R3, resistance R9, sampling resistance Rf and reference voltage circuit; Composed of voltage regulator U2, resistor R2, and resistors R4, R5, and R6 connected in series in series; the anode of the three-terminal reference voltage regulator U2, the base of transistor Q3, one end of resistor R6, and one end of sampling resistor Rf are shared and formed Common contact, the common contact is the sampling current input terminal of the constant voltage and constant current control circuit; the emitter of the transistor Q3 is in line with the other end of the sampling resistor Rf to form a common contact, which is the constant voltage and constant current control circuit The sampling current output terminal of the three-terminal reference voltage source U2, the cathode of the three-terminal reference voltage source U2, one end of the resistor R2, one end of the resistor R4, and the second non-inverting input port of the dual voltage comparator U1 are collinear; the reference level of the three-terminal reference voltage source U2 , the other end of the resistor R6 and one end of the resistor R5 are collinear; the first inverting input terminal of the dual voltage comparator U1, the anode of the diode D1 and one end of the resistor R9 are collinear; the other end of the resistor R9 and the other end of the resistor R4 and the other end of the resistor R5 are in line; the power supply end of the dual voltage comparator U1 is in line with the other end of the resistor R2 of the reference voltage circuit to form a common contact, which is the power supply end of the constant voltage constant current control circuit; the resistor One end of R1 is the first control signal output end of the constant-voltage constant-current control circuit; the other end of the resistor R1 is electrically connected to the first output end of the dual-voltage comparator U1; one end of the resistor R3 is the constant-voltage constant-current control circuit The second control signal output end of the resistor R3; the other end of the resistor R3, the anode of the diode D2, and the second output end of the dual voltage comparator U1 are in line; the cathode of the diode D2, the cathode of the diode D1, and the collector of the transistor Q3 are in line; The first non-inverting input terminal and the second inverting input terminal of the dual-voltage comparator U1 are jointly used as the sampling voltage input terminal of the constant voltage constant current control circuit.

The capacitance values of the voltage dividing capacitors C1 to Cn and the filter energy storage capacitor Co of the above-mentioned voltage dividing and discharging circuits of each stage are equal.

The positive effects of the present invention are: the present invention uses conventional crystal transistors, crystal diodes, comparators, regulator tubes, resistors, capacitors and other components, and realizes voltage stabilization without a transformer through circuit design. The constant current DC output drives the power supply for lighting LEDs or LED groups in series. Since the transformer is omitted, the volume of the power supply is reduced, the weight is reduced, and the cost is reduced.

Description of drawings

Fig. 1 is a kind of circuit block diagram of the present invention;

Fig. 2 is the electrical schematic diagram of Fig. 1;

Fig. 3 is the equivalent circuit diagram of the voltage-dividing discharge circuit at all levels in Fig. 2 during the positive half cycle of alternating current;

FIG. 4 is an equivalent circuit diagram of the voltage-dividing discharge circuit of each stage in FIG. 2 in the negative half cycle of alternating current.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Referring to Fig. 1, the LED power supply for lighting without a transformer of the present invention is composed of a main circuit 1, a constant voltage constant current control circuit 2 and an LED power supply interface J1. The LED power supply interface J1 has a positive pole and a negative pole; the main circuit 1 is provided with an AC input terminal A1, a DC power supply output terminal A2, a first control signal input terminal A3, a second control signal input terminal A4, and a constant voltage constant current control circuit power supply output terminal A5; the constant voltage and constant current control circuit 2 is provided with a sampling voltage input terminal B2, a first control signal output terminal B3, a second control signal output terminal B4, a power supply terminal B5, a sampling current input terminal B6 and a sampling current output terminal B7; The sampling voltage input terminal B2 of the voltage constant current control circuit 2 is electrically connected to the DC power supply output terminal A2 of the main circuit 1; the first control signal input terminal A3 of the main circuit 1 is connected to the first control signal output terminal of the constant voltage constant current control circuit 2 Terminal B3 is electrically connected; the second control signal input terminal A4 of the main circuit 1 is electrically connected with the second control signal output terminal B4 of the voltage-stabilizing and constant-current control circuit 2; the voltage-stabilizing and constant-current control circuit power output terminal A5 of the main circuit 1 is The power terminal B5 of the constant voltage and constant current control circuit 2 is electrically connected; the sampling current input terminal B6 of the constant voltage and constant current control circuit 2 is electrically connected to the negative pole of the LED power interface J1; the sampling current output terminal B7 of the constant voltage and constant current control circuit 2 grounding; the positive pole of the LED power interface J1 is electrically connected to the DC power output terminal A2 of the main circuit 1 .

As shown in Fig. 2, the aforementioned main circuit 1 is composed of a voltage dividing discharge circuit, a filter energy storage capacitor Co, a first electronic switch Q1, a second electronic switch Q2, a diode Do2, a freewheeling diode Do1 and an inductance coil L1;

The voltage division discharge circuit has n levels, and the voltage division discharge circuits of all levels are electrically connected in sequence; the voltage division discharge circuits of each level are composed of a voltage division capacitor, a rectifier diode and two isolation diodes. Each stage of the voltage dividing discharge circuit has an input terminal, a first common line terminal, a first output terminal, a second output terminal and a ground terminal. The voltage dividing capacitor is an electrolytic capacitor; the two isolation diodes are divided into a first isolation diode and a second isolation diode. The positive pole of the rectifier diode is the input terminal; the negative pole of the rectifier diode, the positive pole of the second isolation diode, and the positive pole of the voltage dividing capacitor are collinear to form a common contact, which is the first common line terminal; The negative pole of the capacitor and the negative pole of the first isolation diode are electrically connected to form a common contact, which is the first output terminal; the negative pole of the second isolation diode is the second output terminal; the positive pole of the first isolation diode is the ground terminal . The ground terminals of the voltage-dividing discharge circuits at all levels jointly form the ground terminal of the main circuit 1 . Wherein, the first stage voltage dividing discharge circuit of the main circuit 1 is composed of a diode D12 as a rectifier diode, an electrolytic capacitor C1 as a voltage dividing capacitor, a diode D11 as a first isolation diode, and a diode D13 as a second isolation diode. The anode of the diode D12 is not only the input terminal of the first stage voltage dividing discharge circuit, but also the AC input terminal A1 of the main circuit 1 . The second-stage voltage-dividing discharge circuit of the main circuit 1 is composed of an electrolytic capacitor C2 as a voltage-dividing capacitor, a diode D22 as a rectifier diode, a diode D21 as a first isolation diode, and a diode D23 as a second isolation diode. The anode of the diode D22 is the input end of the second-stage voltage dividing and discharging circuit, and the input end is electrically connected to the first output end of the first-stage voltage dividing and discharging circuit. The nth stage voltage dividing discharge circuit of the main circuit 1 is composed of a diode Dn2 as a rectifier diode, an electrolytic capacitor Cn as a voltage dividing capacitor, a diode Dn1 as a first isolation diode, and a diode Dn3 as a second isolation diode. The anode of the diode Dn2 is the input end of the nth stage voltage divider discharge circuit, and the input end is electrically connected to the first output end of the upper stage, that is, the n-1th stage voltage divider discharge circuit. The cathode of the diode Dn2, the anode of the electrolytic capacitor Cn and the anode of the diode Dn3 are collinear to form a common contact.

The second output ends of the voltage-dividing discharge circuits at all levels are connected to the input end of the first electronic switch Q1; the output end of the first electronic switch Q1, one end of the inductance coil L1 and the negative pole of the freewheeling diode Do1 are in line; the freewheeling diode The positive pole of Do1 is grounded; the other end of the inductance coil L1, the positive pole of the filter energy storage capacitor Co and the negative pole of the diode Do2 are collinear to form a common contact, which is the DC power output terminal A2 of the main circuit 1; the filter energy storage capacitor The negative pole of Co and the output terminal of the second electronic switch Q2 are all grounded; the positive pole of the diode Do2 and the input terminal of the second electronic switch Q2 are all electrically connected with the first output terminal of the nth stage voltage divider discharge circuit; the first electronic switch Q1 The control terminal of the second electronic switch Q2 is the first control signal input terminal A3 of the main circuit 1 ; the control terminal of the second electronic switch Q2 is the second control signal input terminal A4 of the main circuit 1 .

The aforementioned first electronic switch Q1 can be an NPN transistor, a PNP transistor, or a common-collector circuit composed of two PNP transistors; this embodiment is preferably a common-collector circuit composed of two PNP transistors. circuit. When the first electronic switch Q1 is an NPN transistor, the base of the NPN transistor is the control terminal of the first electronic switch Q1, and the collector of the NPN transistor is the input terminal of the first electronic switch Q1. The emitter of the transistor is the output terminal of the first electronic switch Q1; when the first electronic switch Q1 is a PNP transistor, the base of the PNP transistor is the control terminal of the first electronic switch Q1, and the PNP transistor The emitter of the first electronic switch is the input terminal of the first electronic switch Q1, and the collector of the PNP transistor is the output terminal of the first electronic switch Q1; when the first electronic switch Q1 is a common collector composed of two PNP transistors- In the common collector circuit, the base of the composite tube circuit is the control terminal of the first electronic switch Q1, the emitter of the composite tube circuit is the input terminal of the first electronic switch Q1, and the collector of the composite tube circuit is the an output terminal of the first electronic switch Q1;

The second electronic switch Q2 can be an NPN transistor, a PNP transistor or a common-collector circuit composed of two PNP transistors. In this embodiment, a common collector-common collector circuit composed of two PNP transistors is preferred. When the second electronic switch Q2 is an NPN transistor, the base of the NPN transistor is the control terminal of the second electronic switch Q2, and the collector of the NPN transistor is the input terminal of the second electronic switch Q2. The emitter of the transistor is the output terminal of the second electronic switch Q2; when the second electronic switch Q2 is a PNP transistor, the base of the PNP transistor is the control terminal of the second electronic switch Q2, and the PNP transistor The emitter of the second electronic switch Q2 is the input end of the second electronic switch, and the collector of the PNP transistor is the output end of the second electronic switch Q2; when the second electronic switch Q2 is a common collector composed of two PNP transistors- In the common collector circuit, the base of the composite tube circuit is the control terminal of the second electronic switch Q2, the emitter of the composite tube circuit is the input terminal of the second electronic switch Q2, and the collector of the composite tube circuit is The output end of the second electronic switch Q2. The aforementioned voltage stabilizing constant current control circuit 2 is composed of a dual voltage comparator U1, an NPN transistor Q3, a diode D1, a diode D2, a resistor R1, a resistor R3, a resistor R9, a sampling resistor Rf and a reference voltage circuit. The reference voltage circuit consists of three It is composed of terminal reference voltage stabilizer U2, resistor R2 and resistor R4, resistor R5 and resistor R6 connected in series in sequence.

In this embodiment, the model of the dual voltage comparator U1 is preferably LM393. The model of the three-terminal reference voltage regulator U2 is preferably LM431A. The dual-voltage comparator U1 of LM393 has two built-in comparators with 1 to 8 pins. The VCC terminal is 8 pins, the VSS terminal is 4 pins, the first non-inverting input terminal is 3 pins, and the first inverting input terminal is 3 pins. 2 pins, the first output end is 1 pin; the second non-inverting input end is 5 pins, the second inverting input end is 6 pins, and the second output end is 7 pins.

The anode of the three-terminal reference stabilized voltage source U2, the base of the triode Q3, one end of the resistor R6 and one end of the sampling resistor Rf have a common contact, which is the sampling current input terminal B6 of the voltage stabilizing constant current control circuit 2; the triode The emitter of Q3 and the other end of the sampling resistor Rf have a common contact, which is the sampling current output terminal B7 of the constant voltage and constant current control circuit 2; the cathode of the three-terminal reference voltage stabilizer U2 and one end of the resistor R2, One end of R4 and the second non-inverting input pin 5 of the dual-voltage comparator U1 have a common contact; the reference level of the three-terminal reference voltage regulator U2, the other end of the resistor R6, and one end of the resistor R5 are in line; the dual-voltage comparator U1 The first inverting input terminal 2 pin of the diode D1, the positive pole of the diode D1 and one end of the resistor R9 are in line; the other end of the resistor R9, the other end of the resistor R4, and the other end of the resistor R5 are in line; the power supply end of the dual voltage comparator U1 That is to say, pin 8 of the VCC terminal and the other end of the resistor R2 of the reference voltage circuit have a common contact, which is the power supply terminal B5 of the constant voltage and constant current control circuit 2; one end of the resistor R1 is the constant voltage and constant current control circuit 2 The first control signal output terminal B3 of the resistor R1; the other end of the resistor R1 is electrically connected to the first output pin 1 of the dual voltage comparator U1; one end of the resistor R3 is the second control signal output terminal of the constant voltage constant current control circuit 2 B4; the other end of the resistor R3, the positive pole of the diode D2, and the second output terminal 7 of the dual-voltage comparator U1 are collinear; the negative pole of the diode D2, the negative pole of the diode D1, and the collector of the transistor Q3 are collinear; the dual-voltage comparator Pin 3 of the first non-inverting input terminal of U1 and pin 6 of the second inverting input terminal are both the sampling voltage input terminal B2 of the constant voltage constant current control circuit 2 . The pin 4 of the VSS end of the dual voltage comparator U1 is grounded.

In this embodiment, the aforementioned voltage dividing capacitors C1 , C2 . . . Cn and filter energy storage capacitor Co are all electrolytic capacitors, and their capacitance values are all equal.

See Fig. 2, referring to Fig. 3 and Fig. 4, the working principle and mode of the light-emitting diode power supply for lighting without a transformer of the present embodiment are as follows:

The LED lamp bead or the LED lamp bead group connected in series is electrically connected to the LED power interface J1 of the transformerless light-emitting diode power supply for lighting in this embodiment.

The external 220V alternating current AC is input through the alternating current input terminal A1 of the main circuit 1. During the positive half cycle of the alternating current AC, the current passes through D12, C1, D22, C2, ... Dn2, Cn, Do2, Co to C1, C2, ... Cn-1, Cn, and Co capacitors are charged. During the charging cycle, according to the circuit principle, D11, D13, D21, D23, ... Dn1, Dn3 in the circuit do not work. The charging equivalent circuit is shown in Figure 3.

When charging, the output voltage on the filter energy storage capacitor Co provides the working voltage for the LED and provides the sampling voltage for the constant voltage and constant current control circuit 2. The voltage limit control of the output voltage on the filter energy storage capacitor Co is output through the dual voltage comparator U1. The voltage Vout is compared with the reference voltage Vref1: when Vout>Vref1, the first output pin 1 of the dual voltage comparator U1 outputs a low level, and at the same time, when the charging current is greater than the set current, the sampling resistor Rf The increase in voltage drop means that the base voltage of the triode increases to turn on the transistor Q3, both of which lead to the conduction of the transistor Q2, and after the transistor Q2 is turned on, the diode Do2 and the capacitor Co are bypassed, thereby stopping the charging of the capacitor Co, ensuring The output voltage Vout will not be greater than Vref1 and the output current will not be greater than the set current.

When the 220V alternating current AC is in the negative half cycle, the circuit stops charging each capacitor and enters the current consumption cycle. In the current consumption cycle, according to the circuit principle, the voltage dividing capacitors are transformed into a parallel circuit. The equivalent circuit diagram is shown in Figure 4 . The output voltage on the filter energy storage capacitor Co provides the working voltage for the LED and provides the sampling voltage for the constant current control circuit. The voltage limit control of the output voltage on the filter energy storage capacitor Co is controlled by the dual voltage comparator U1 for Vout and Vref2. By comparison, when Vout<Vref2, pin 1 of the first output terminal of the dual-voltage comparator U1 outputs a low level, making Q1 turn on, and connecting the voltage dividing capacitors C1~Cn to make them be connected in parallel to supplement and charge Co, and divide the voltage Capacitor C1 forms a discharge circuit from its positive pole to the negative pole of capacitor C1 through D13, Q1, L1, Co, D11 to supplement the current for Co. The current is constant to ensure that the Vout output will not be less than Vref2. The constant current control of the output current of the DC power supply during supplementary charging is realized through Q3. When the current flowing through the sampling resistor Rf exceeds the set current, the voltage drop reaches 0.7V, Q3 is turned on, and is in phase with the collector of Q3. The connected diode D1 pulls down the first negative input terminal of the dual-voltage comparator U1, prohibits the first output terminal of the dual-voltage comparator U1 from outputting low voltage, prevents the triode Q1 from conducting, and stops supplementing the power filter energy storage capacitor Co Charging, since the first negative input terminal of the dual-voltage comparator U1 is connected to the reference voltage Vref2 through R9, pulling down the first negative input terminal of the dual-voltage comparator U1 will not affect the reference voltage Vref2; at the same time The diode D2 connected to the collector of Q3 pulls the base of Q2 low, so that Q2 is turned on, Do2 and Co are bypassed, and the supplementary charging of the power filter energy storage capacitor Co is stopped. The authority of the constant current control is higher than that of the voltage limiting control, and the voltage limiting control does not work when Q3 is turned on.

According to the following steps, determine the selection of related parameters of the LED power supply for transformerless lighting in the embodiment of the present invention as shown in Figure 2:

First determine the output voltage value Vout and current value I of the LED power supply for lighting:

Vout=LEDs*3.5 (1)

I=0.3A (2)

Vout is the output voltage value of the DC power supply, and LEDs is the number of lighting LEDs that need to be driven. The forward voltage drop of a 1 watt lighting LED is generally 3.5V, and the current I is 300mA.

The resistance value of the sampling resistor Rf can be determined by the LED constant current control value I, and the Rf is 2.3 ohms calculated according to the formula (3)

Rf=0.7/I(3)

The reference voltage is provided by the three-terminal reference voltage regulator U2, and the resistance values of R4, R5, and R6 are selected to determine the voltage values of the reference voltages Vref1 and Vref2. In the application, R6 can generally be selected as 2.5K ohms. R4 determines the allowable error difference of the DC output voltage V out. In applications, it can generally be selected as 200 ohms. R5 can be calculated according to formula (4). The voltage values of Vref1 and Vref2 are determined according to calculation formulas (5) and (6).

R5=R6*Vout/2.5-R6-R4/2(4)

Vref1=2.5*(R4+R5+R6)/R6 (5)

Vref2=2.5*(R5+R6)/R6(6)

The number of stages n of the voltage-dividing discharge circuit of the main circuit 1, that is, the selection of the number of voltage-dividing capacitors, how many stages of voltage-dividing capacitors to choose can be calculated by formula (7) according to Vout determined by formula (1):

n=(Vac–Vout)/(m * Vout ) (7)

The value range of the coefficient m is 1 to 6. According to experience, select the voltage dividing capacitors C1, C2...Cn and the filter energy storage capacitor Co to have the same capacitance, and the best selection range for the voltage dividing capacitor voltage is between 1.5 and 3 times the output voltage Vout, and you can get better performance. For a good DC constant current and voltage-limited output, that is, the optimal value range of m is between 1.5 and 3, so that the number n of voltage-dividing capacitors can be determined. Taking the input AC voltage of 220V as an example, if the number of LEDs to be driven is 4, the output DC voltage Vout is calculated according to the formula (1) to be 14V. If m is 1, n can be calculated as 15; if m is 6, Then it can be calculated that n is 2; if m is determined to be 2 between 1.5 and 3 in the optimal value range of m, then n can be calculated as 7, that is to say, 7 voltage dividing capacitors are selected in the main circuit 1, and through this implementation The circuit of this example can drive 4 LEDs of this example, and the working current and voltage are the most stable.

The above embodiments are descriptions of specific implementations of the present invention, rather than limitations of the present invention. Those skilled in the relevant technical fields can also make various transformations and changes without departing from the spirit and scope of the present invention. Corresponding equivalent technical solutions, therefore all equivalent technical solutions should fall into the patent protection scope of the present invention.

Claims (1)

1. a transless LED for illumination power supply, is characterized in that: comprise main circuit (1), pressure-stabilizing constant flow control circuit (2) and LED power interface (J1); Described LED power interface (J1) has positive pole and negative pole; Described main circuit (1) is provided with alternating current input (A1), DC power output end (A2), the first control signal input (A3), the second control signal input (A4) and pressure-stabilizing constant flow control circuit power output end (A5); Described pressure-stabilizing constant flow control circuit (2) is provided with sampling voltage input (B2), the first control signal output (B3), the second control signal output (B4), power end (B5), sampling current input (B6) and sampling current output (B7); The sampling voltage input (B2) of described pressure-stabilizing constant flow control circuit (2) is electrically connected with the DC power output end (A2) of main circuit (1); First control signal input (A3) of main circuit (1) is electrically connected with the first control signal output (B3) of pressure-stabilizing constant flow control circuit (2); Second control signal input (A4) of main circuit (1) is electrically connected with the second control signal output (B4) of pressure-stabilizing constant flow control circuit (2); The pressure-stabilizing constant flow control circuit power output end (A5) of main circuit (1) is electrically connected with the power end (B5) of pressure-stabilizing constant flow control circuit (2); The sampling current input (B6) of pressure-stabilizing constant flow control circuit (2) is connected with the negative electricity of LED power interface (J1); Sampling current output (B7) ground connection of pressure-stabilizing constant flow control circuit (2); The positive pole of LED power interface (J1) is electrically connected with the DC power output end (A2) of main circuit (1); Described main circuit (1) be a kind of when the positive half cycle of input AC electricity by some spaced rectifier diodes and derided capacitors series connection dividing potential drop and filtering energy storage capacitor Co produce direct current export, at input AC electricity negative half period time by corresponding isolating diode, the first shared electronic switch Q1 and inductance coil L1, electric discharge is supplemented to filtering energy storage capacitor Co successively by each derided capacitors and produces the circuit that direct current exports; Described pressure-stabilizing constant flow control circuit (2) is by carrying out sampling voltage signal and sampling current signal processing rear feedback effect in described main circuit (1) to ensure the direct voltage that main circuit (1) exports and the stable circuit of direct current;

Described main circuit (1) comprises dividing potential drop discharge circuit, filtering energy storage capacitor Co, the first electronic switch Q1, the second electronic switch Q2, diode Do2, sustained diode o1 and inductance coil L1;

Dividing potential drop discharge circuit has n level, and dividing potential drop discharge circuit at different levels is electrically connected successively; Dividing potential drop discharge circuit at different levels is by derided capacitors, rectification diode and 2 isolating diode compositions; Dividing potential drop discharge circuit at different levels all has input, the first conllinear end, the first output, the second output and ground; Derided capacitors is electrochemical capacitor; 2 isolating diodes are divided into the first isolating diode and the second isolating diode; The positive pole of rectification diode is input; The negative pole of rectification diode, the positive pole of the second isolating diode, the positive pole conllinear of derided capacitors and form common junction, this common junction is the first conllinear end; The negative pole of derided capacitors is connected with the negative electricity of the first isolating diode and forms common junction, and this common junction is the first output; The negative pole of the second isolating diode is the second output; The positive pole of the first isolating diode is earth terminal; Wherein, the 1st fraction pressure discharge circuit of main circuit (1) is made up of the diode D12 as rectifier diode, the electrochemical capacitor C1 as derided capacitors, the diode D11 as the first isolating diode and the diode D13 as the second isolating diode; The positive pole of diode D12 had both been the input of the 1st fraction pressure discharge circuit, was also the alternating current input (A1) of main circuit (1); N-th fraction pressure discharge circuit of main circuit (1) is made up of the diode Dn2 as rectifier diode, the electrochemical capacitor Cn as derided capacitors, the diode Dn1 as the first isolating diode and the diode Dn3 as the second isolating diode; The positive pole of diode Dn2 is the input of the n-th fraction pressure discharge circuit, and this input and upper level are also that the (n-1)th fraction presses the first output of discharge circuit to be electrically connected; The positive pole conllinear of the negative pole of diode Dn2, the positive pole of electrochemical capacitor Cn and diode Dn3 and form common junction, this common junction is the first conllinear end, is also the pressure-stabilizing constant flow control circuit power output end (A5) of main circuit (1);

Second output of dividing potential drop discharge circuit at different levels is all connected to the input of the first electronic switch Q1; The negative pole conllinear of the output of the first electronic switch Q1, one end of inductance coil L1 and sustained diode o1; The plus earth of sustained diode o1; The other end of inductance coil L1, the positive pole of filtering energy storage capacitor Co and the negative pole conllinear of diode Do2 and form common junction, this common junction is the DC power output end (A2) of main circuit (1); The negative pole of filtering energy storage capacitor Co and the equal ground connection of output of the second electronic switch Q2; The positive pole of diode Do2 and the input of the second electronic switch Q2 all press the first output of discharge circuit to be electrically connected with the n-th fraction; The control end of the first electronic switch Q1 is the first control signal input (A3) of main circuit (1); The control end of the second electronic switch Q2 is the second control signal input (A4) of main circuit (1);

The progression n of the dividing potential drop discharge circuit of main circuit (1) is according to calculating formula n=(Vac – Vout)/(m ×vout )calculate, wherein Vac is the alternating voltage inputted to the positive pole of diode D12, and Vout is the direct voltage exported at the positive pole of filtering energy storage capacitor Co, and the span of m is 1 to 6;

The first described electronic switch Q1 is NPN type triode, PNP type triode or common collection-altogether collector of being made up of 2 PNP type triode; When the first electronic switch Q1 is NPN type triode, the base stage of this NPN type triode is the control end of the first electronic switch Q1, the collector electrode of this NPN type triode is the input of the first electronic switch Q1, and the emitter of this NPN type triode is the output of the first electronic switch Q1; When the first electronic switch Q1 is PNP type triode, the base stage of this PNP type triode is the control end of the first electronic switch Q1, the emitter of this PNP type triode is the input of the first electronic switch Q1, and the collector electrode of this PNP type triode is the output of the first electronic switch Q1; When the first electronic switch Q1 is the common collection-common collector be made up of 2 PNP type triode, the base stage of the common collection-common collector of these 2 PNP type triode compositions is the control end of the first electronic switch Q1, the emitter of the common collection-common collector of these 2 PNP type triode compositions is the input of the first electronic switch Q1, and the collector electrode of the common collection-common collector of these 2 PNP type triode compositions is the output of the first electronic switch Q1;

The second described electronic switch Q2 is NPN type triode, PNP type triode or common collection-altogether collector of being made up of 2 PNP type triode; When the second electronic switch Q2 is NPN type triode, the base stage of this NPN type triode is the control end of the second electronic switch Q2, the collector electrode of this NPN type triode is the input of the second electronic switch Q2, and the emitter of this NPN type triode is the output of the second electronic switch Q2; When the second electronic switch Q2 is PNP type triode, the base stage of this PNP type triode is the control end of the second electronic switch Q2, the emitter of this PNP type triode is the input of the second electronic switch Q2, and the collector electrode of this PNP type triode is the output of the second electronic switch Q2; When the second electronic switch Q2 is the common collection-common collector be made up of 2 PNP type triode, the base stage of the common collection-common collector of these 2 PNP type triode compositions is the control end of the second electronic switch Q2, the emitter of the common collection-common collector of these 2 PNP type triode compositions is the input of the second electronic switch Q2, and the collector electrode of the common collection-common collector of these 2 PNP type triode compositions is the output of the second electronic switch Q2;

Described pressure-stabilizing constant flow control circuit (2) comprises twin voltage comparator U1, triode Q3, diode D1, diode D2, resistance R1, resistance R3, resistance R9, sampling resistor Rf and reference voltage circuit; Described reference voltage circuit is made up of three end reference voltage stabilizing source U2, resistance R2 and the resistance R4 connected successively, resistance R5 and resistance R6; One end of the anode of three end reference voltage stabilizing source U2, the base stage of triode Q3, one end of resistance R6 and sampling resistor Rf is shared and forms common junction, and this common junction is the sampling current input (B6) of pressure-stabilizing constant flow control circuit (2); The emitter of triode Q3 and the other end conllinear of sampling resistor Rf and form common junction, this common junction is the sampling current output (B7) of pressure-stabilizing constant flow control circuit (2); The second in-phase input end conllinear of the negative electrode of three end reference voltage stabilizing source U2, one end of resistance R2, one end of resistance R4 and twin voltage comparator U1; The reference level of three end reference voltage stabilizing source U2, the other end of resistance R6 and one end conllinear of resistance R5; One end conllinear of first inverting input of twin voltage comparator U1, the positive pole of diode D1 and resistance R9; The other end conllinear of the other end of resistance R9, the other end of resistance R4 and resistance R5; The other end conllinear of the power end of twin voltage comparator U1 and the resistance R2 of reference voltage circuit and form common junction, this common junction is the power end (B5) of pressure-stabilizing constant flow control circuit (2); One end of resistance R1 is the first control signal output (B3) of pressure-stabilizing constant flow control circuit (2); The other end of resistance R1 is electrically connected with first output of twin voltage comparator U1; One end of resistance R3 is the second control signal output (B4) of pressure-stabilizing constant flow control circuit (2); The second output conllinear of the other end of resistance R3, the positive pole of diode D2 and twin voltage comparator U1; The collector electrode conllinear of the negative pole of diode D2, the negative pole of diode D1 and triode Q3; First in-phase input end of twin voltage comparator U1 and the second inverting input are jointly as the sampling voltage input (B2) of pressure-stabilizing constant flow control circuit (2);

The resistance value of described sampling resistor Rf is determined by following formula:

Rf=0.7/I, in formula, I is the current value that transless LED for illumination power supply exports;

The capacitance of the electrochemical capacitor C1 to Cn as derided capacitors in described dividing potential drop discharge circuits at different levels and filtering energy storage capacitor Co is all equal.