CN204069452U - No-strobe LED constant current drive control circuit based on APFC - Google Patents

Abstract

The utility model discloses a kind of based on APFC without stroboscopic LED constant current Drive and Control Circuit, it comprises APFC constant-voltage control circuit unit, constant-current control circuit unit, output voltage adaptation control circuit unit and biasing circuit unit; Described constant-current control circuit unit is by output current sample resistance Rs, reference voltage source , error amplifier EA and power MOS pipe Q forms; Described output voltage adaptation control circuit unit is made up of isolating diode D2, filter LPF and output signal divider resistance R6; Described biasing circuit unit is to error amplifier EA, reference voltage source there is provided biased.The utility model can use less output filter capacitor, and there will not be 100/120Hz low frequency flicker phenomenon.The utility model improves the adaptability to changes to electrical network glitch, and its cost is low, stable and reliable working performance, is with a wide range of applications and promotional value.

Description

No-strobe LED constant current drive control circuit based on APFC

technical field

The utility model relates to an LED lighting drive circuit, in particular to an APFC-based LED constant current drive control circuit.

Background technique

LED light source has the advantages of environmental protection, energy saving, long service life, low driving voltage, etc., and is recognized as the most promising lighting source in the 21st century.

In the medium and high-power LED lighting fixtures powered by mains, it is always hoped that the power factor PF of the lamps is as close as possible to 1, so as to reduce the harmonic distortion of the supply current, reflect the energy-saving characteristics of LED lamps, and avoid polluting the mains network .

Although the power of most LED lamps is below 80W, it seems that the APFC single-tube flyback converter with few components and low cost can be used as the driving power of the LED chip in the lamp. However, the output voltage of the APFC single-tube flyback converter The inherent 100/120Hz AC ripple voltage causes LED lamps to have 100/120Hz stroboscopic phenomenon. Although it is not noticed by human eyes, consumers still have a lot of concerns, which limits the application of LED lamps unless a large capacity The output filter capacitor reduces the amplitude of the 100/120Hz AC ripple voltage, so that it is possible to weaken the strobe to a level that general digital cameras cannot perceive.

When using the existing LED drive control circuit shown in Figure 1 to drive an LED lamp with a power of 30W, for 15 LED chips connected in series, in order to avoid flickering, according to the volt-ampere characteristics of the LED chip, it is required that 100/ 120Hz AC ripple voltage peak-to-peak <15×5mV, the output filter capacitor capacity is about 30000μF. However, the space of LED lamps is small, and it is impossible to place such a large-capacity capacitor; in addition, the output filter capacitor is too large to affect the response speed of the APFC converter. As a result, Boost-based APFC+flyback or (+LLC), APFC flyback+DC-DC constant current two-stage converter topology is forced to be used in high-power (25W or above) LED lamp driving power supply in order to obtain no flicker LED lamps with high power factor PF - this will inevitably increase the cost and volume of the driving power supply, and also reduce the reliability and efficiency of the driving power supply.

The State Intellectual Property Office published a patent document with the publication number CN102202449A on September 28, 2011, and the patent name is LED drive control circuit and method. This patent document includes a voltage comparison module, which generates a comparison signal PWM for output current threshold control. module and the LED driver module; the output current threshold control module generates the current threshold control signal IREF/VREF according to the duty ratio of the comparison signal PWM to the LED driver module; the LED driver module controls the signal IREF/VREF according to the input current threshold and compares The signal PWM generates an LED drive control signal; the product of the current threshold control signal IREF/VREF and the duty ratio of the comparison signal PWM is a constant, so that under the comparison signal PWM with different duty ratios, the LED drive control circuit outputs The average current is the same. The utility model solves the influence of the excessive change of the current of the LED lamp when the mains power changes, facilitates the setting of the output current, and solves the problem of the flickering of the LED lamp caused by the change of the current.

The above-mentioned patent application documents are different from the technical solutions of this patent.

Contents of the invention

The purpose of the utility model is to overcome the deficiency of the existing APFC-based LED drive circuit, and provide an APFC-based LED constant current drive control circuit whose output voltage without 100/120Hz flicker is controlled by the LED load voltage. The control circuit does not appear 100/120Hz low-frequency flicker phenomenon, and improves the resilience to power grid transient interference.

In order to achieve the above object, the technical solution adopted in the utility model is:

The non-stroboscopic LED constant current drive control circuit based on APFC, it comprises APFC constant voltage control circuit unit, constant current control circuit unit, output voltage adaptive control circuit unit and bias circuit unit; Described constant current control circuit unit is outputted by Current sampling resistor Rs, reference voltage source , error amplifier EA and power MOS transistor Q, one end of the output current sampling resistor Rs is respectively connected to the source S of the power MOS transistor Q and the inverting input end of the error amplifier EA, and the other end is connected to the common potential reference point of the secondary circuit, the error The output terminal of the amplifier EA is connected to the gate G of the power MOS transistor Q; the output voltage adaptive control circuit unit is composed of an isolation diode D2, a filter LPF and an output signal voltage dividing resistor R6, and the positive pole of the isolation diode D2 is connected to the power MOS transistor The drain D of Q, the drain D of the power MOS transistor Q is also connected to the negative pole of the LED series chipset, the positive pole of the LED series chipset is connected to the voltage output terminal of the APFC constant voltage control circuit unit, and the isolation diode D2 The negative pole of the negative pole connects the input terminal of low-pass filter LPF, and the output signal of low-pass filter LPF connects the voltage sampling point of described APFC constant voltage control circuit unit through resistance R6; Described bias circuit unit gives error amplifier EA, reference power source Provide bias.

The constant current control circuit unit, the output voltage self-adaptive control circuit unit and the bias circuit unit may be independent components, or may be partially or entirely integrated components.

The APFC constant voltage control circuit unit adopts an APFC single-tube flyback constant voltage source circuit.

The APFC constant voltage control circuit unit adopts a step-up APFC circuit.

The beneficial effects of the utility model:

1. The non-flicker APFC constant current output control mode provided by the utility model can use a smaller output filter capacitor under the condition of parameter matching, and there will be no 100/120Hz low-frequency flicker phenomenon.

2. It has little effect on the overall efficiency of the lamp, and the total loss is lower than that of the LED drive power supply with two-stage topology.

3. Effectively suppress the sudden change of the current of the LED series chipset caused by the transient interference of the power grid caused by the slow output response speed of the APFC, and improve the resilience to the transient interference of the power grid.

4. The control circuit has few components, low cost, and can automatically adapt to different The most valuable LED chip greatly improves the production efficiency of LED lamps.

5. Practice shows that the flicker-free control mode provided by the utility model works stably and reliably. It has broad application prospects and promotion value in medium and high-power LED lighting fixtures.

Description of drawings

Below in conjunction with accompanying drawing and specific embodiment the utility model is described in further detail:

Fig. 1 is the electrical schematic diagram of prior art;

Fig. 2 is the electrical schematic diagram of the utility model embodiment 1;

Fig. 3 is the electrical principle diagram of the utility model embodiment 2.

In the figure: 1. APFC constant voltage control circuit unit; 2. Constant current control circuit unit; 3. Output voltage adaptive control circuit unit; 4. Bias circuit unit; 5. LED series chipset; 6. Rectification filter circuit unit .

Detailed ways

Example 1:

The APFC constant voltage control circuit unit in the APFC-based flicker-free LED constant current drive control circuit adopts an APFC single-tube flyback constant voltage source circuit.

As shown in Figure 2, the flicker-free LED constant current drive control circuit based on APFC includes APFC constant voltage control circuit unit 1, constant current control circuit unit 2, output voltage adaptive control circuit unit 3 and bias circuit unit 4 .

The constant current control circuit unit 2 is composed of an output current sampling resistor Rs, a reference voltage source , error amplifier EA and power MOS transistor Q, one end of the output current sampling resistor Rs is respectively connected to the source S of the power MOS transistor Q and the inverting input end of the error amplifier EA, and the other end is connected to the common potential reference point of the secondary circuit, the error The output terminal of the amplifier EA is connected to the gate G of the power MOS transistor Q.

The output voltage adaptive control circuit unit 3 is composed of an isolation diode D2, a filter LPF and an output signal voltage dividing resistor R6, the anode of the isolation diode D2 is connected to the drain D of the power MOS transistor Q, and the drain D of the power MOS transistor Q It is also connected to the negative pole of the LED series chipset 5, the positive pole of the LED series chipset is connected to the voltage output end of the APFC constant voltage control circuit unit, and the negative pole of the isolation diode D2 is connected to the input end of the low-pass filter LPF, low The output signal of the pass filter LPF is connected to the voltage sampling point of the APFC constant voltage control circuit unit through the resistor R6.

Described bias circuit unit 4 gives error amplifier EA, reference voltage source Provide bias. The constant current control circuit unit, the output voltage self-adaptive control circuit unit and the bias circuit unit may be independent components, or may be partially or entirely integrated components.

In this example, the output power of the LED lamp is 36W, the internal connection mode is 15 series and 5 parallel, the no-load output voltage is 52V, and the load current 750mA. The positive terminal of the series-parallel LED chipset is connected to the positive terminal of the rectifier filter circuit, and the negative terminal is connected to the drain of the power MOS tube Q; the capacity of the output filter capacitor C1 is 2×470μF, and the peak-to-peak value of the output ripple voltage About 2.6V, if the reference voltage source 0.45V, the current sampling resistor Rs is 0.33Ω, and the power MOS tube Q is a power MOS tube with a conduction internal resistance of 85mΩ and a withstand voltage of 60V. By adjusting the output signal voltage dividing resistor R6, the DS of the power MOS tube Q is extremely average. DC voltage equal , That is, 1.3V, so that the 100/120Hz strobe is basically eliminated.

Example 2:

As shown in Figure 3, the non-stroboscopic LED constant current drive control circuit based on APFC includes an APFC constant voltage control circuit unit, a constant current control circuit unit, an output voltage adaptive control circuit unit and a bias circuit unit; this embodiment Among them, the APFC constant voltage control circuit unit adopts a step-up APFC circuit. The active power factor correction (APFC) circuit is mainly to connect the active power controller in series between the rectifier and the output capacitor, so that the input current and input voltage of the AC/DC converter are sine waves with the same frequency and phase, so that the power factor is close to 1. , and the output voltage is stable.

Other content is the same as the technical content in Embodiment 1, so no further description will be given.

The working principle of the utility model:

at no load or load current less than the rated value ( ), the error amplifier EA outputs a high voltage, the power MOS transistor Q is turned on, and the voltage drop between the DS poles is very small, the converter output voltage Determined by the APFC constant voltage control circuit unit. When the load current up to the rated value ( ), the constant current control circuit operates, if the output voltage ↑→The voltage of the inverting input terminal of the error amplifier EA↑→The output voltage of the error amplifier EA↓→The DS pole voltage of the power MOS transistor Q ↑→Voltage at both ends of the LED series chipset ↓→Output current ↓; otherwise, the output voltage ↓→The voltage at the inverting input terminal of the error amplifier EA↓→The output voltage of the error amplifier EA↑→The DS pole voltage of the power MOS tube Q ↓→Voltage at both ends of the LED series chipset↑→Output current ↑. It can be seen that the constant current control circuit drops the inherent 100/120Hz AC ripple voltage output by the APFC converter to the DS pole of the power MOS transistor Q, so that the current of the LED series chip set Stabilize, weaken, or even completely eliminate 100/120Hz strobe.

To avoid LED chip Too small, resulting in the power MOS tube Q at full load The voltage drop is too large, resulting in overheating of the power MOS tube Q and reducing the power efficiency; or due to the LED chip Too large, resulting in power MOS tube Q The voltage drop is low, so that the load current Less than the rated value, 100/120Hz strobe cannot be completely eliminated. For this reason, an automatic tracking circuit for the average potential of the drain D of the power MOS transistor Q is set: the drain voltage signal of the power MOS transistor Q is sent to the filter LPF through the isolation diode D2 to remove the 100/120Hz AC ripple voltage, and then connected to the APFC constant voltage control The output voltage sampling point of the circuit unit, so that when the average drain voltage of the power MOS transistor Q↑→APFC constant voltage control circuit unit output voltage sampling point potential↑→output voltage ↓→The average voltage of the drain of the power MOS transistor Q↓; and vice versa, the average potential of the drain of the power MOS transistor Q is finally forced to be stable near the set value, which is related to the capacity of the filter capacitor of the rectifier filter circuit unit 6. The resistance of R6 can change the average potential of the drain D of the MOS transistor Q, when The average voltage is equal to the peak-to-peak value of the 100/120Hz AC ripple voltage in the output DC voltage Halfway through, the strobe just disappears completely.

The above description is only a preferred embodiment of the utility model, and of course it cannot limit the scope of rights of the utility model. Replacement does not depart from the protection scope of the technical solution of the utility model.

Claims (4)

1. A non-stroboscopic LED constant current drive control circuit based on APFC, is characterized in that: it comprises APFC constant voltage control circuit unit, constant current control circuit unit, output voltage adaptive control circuit unit and bias circuit unit; The constant current control circuit unit consists of an output current sampling resistor Rs, a reference voltage source , error amplifier EA and power MOS transistor Q, one end of the output current sampling resistor Rs is respectively connected to the source S of the power MOS transistor Q and the inverting input end of the error amplifier EA, and the other end is connected to the common potential reference point of the secondary circuit, the error The output terminal of the amplifier EA is connected to the gate G of the power MOS transistor Q; The output voltage adaptive control circuit unit is composed of an isolation diode D2, a filter LPF and an output signal voltage dividing resistor R6, the anode of the isolation diode D2 is connected to the drain D of the power MOS transistor Q, and the drain D of the power MOS transistor Q It is also connected to the negative pole of the LED series chipset, the positive pole of the LED series chipset is connected to the voltage output terminal of the APFC constant voltage control circuit unit, the negative pole of the isolation diode D2 is connected to the input end of the low-pass filter LPF, and the low-pass The output signal of the filter LPF is connected to the voltage sampling point of the APFC constant voltage control circuit unit through the resistor R6; Described bias circuit unit gives error amplifier EA, reference voltage source Provide bias. 2. The non-stroboscopic LED constant current drive control circuit based on APFC according to claim 1, characterized in that: the constant current control circuit unit, the output voltage adaptive control circuit unit and the bias circuit unit can be mutually Independent components may also be partially or wholly integrated components. 3. The non-stroboscopic LED constant current drive control circuit based on APFC according to claim 1, characterized in that: the APFC constant voltage control circuit unit adopts an APFC single-tube flyback constant voltage source circuit. 4. The non-stroboscopic LED constant current drive control circuit based on APFC according to claim 1, characterized in that: said APFC constant voltage control circuit unit adopts a step-up APFC circuit.