CN202009514U - Separation-type AC-DC (alternating current-direct current) flyback LED driving power source - Google Patents

Abstract

The utility model relates to a separation-type AC-DC (alternating current -direct current) flyback LED driving power source. The separation-type AC-DC flyback LED driving power source is characterized in that a driving flyback circuit works in an interrupted conduction mode, a design of single-stage power factor correction is adopted so that LED current can be regulated and a power factor approaching 1 (98%) can be realized, efficiency of the overall unit reaches 90% by means of resonant control, accurate constant-voltage and constant-current output can be realized by the aid of the primary control technique without light-coupled devices or constant-voltage and constant-current circuits, and thereby space on a system board can be saved. A load short circuit protection circuit is arranged inside the driving power source. A chip of the separation-type AC-DC flyback LED driving power source is novel in technique, low in components number, small in size, complete in functions and the like, and accordingly the separation-type AC-DC flyback LED driving power source is highly suitable for daily illumination.

Description

A separate AC-DC instead swashs the LED driving power

Technical field

The utility model belongs to the high voltage integrated circuit field, relates to a kind of LED driving power, relates in particular to a kind of separate AC-DC and instead swashs the LED driving power.

Background technology

Under to the constantly progressive background of global energy shortage, environmental requirement, countries in the world are all supported the sustainable green energy conservation illumination of development energetically.The lighting technology that the LED illumination is traditional relatively is a kind of revolutionary energy-saving illumination technology, is in now in the process of develop rapidly.Yet the requirement of LED driving power is also in continuous progress, the crucial evaluation index that high Current Control precision, high reliability, high power, safe isolation, High Power Factor, volume are little, cost substandard etc. becomes the LED power drives.

The LED chip for driving that is used for general illumination at present all needs to use optocoupler in order to realize that higher Current Control precision and primary and secondary limit isolate, owing to used optocoupler, its cost is also higher.If do not use the open loop structure of optocoupler then the Current Control precision is all relatively poor.Appearance of the present invention is not being used under the situation of optocoupler, realizes that simultaneously higher Current Control precision and primary and secondary limit isolate; The present invention has only just finished Current Control with the one-level controller, has power factor emendation function simultaneously concurrently, two-stage control structure is in the past simplified be the one-level control structure; In addition, the present invention effectively raises overall efficiency by adopting quasi-resonance control.

Summary of the invention

The utility model mainly solves existing contradiction between the LED chip for driving cost that is used for general illumination at present and the Current Control precision, also possesses power factor emendation function simultaneously; Provide a kind of separate AC-DC that takes into account chip cost and Current Control precision simultaneously instead to swash the LED chip for driving,, can develop daily LED illuminating products such as being used for room lighting by linking to each other with the output of AC rectification bridge.

Main contents of the present utility model comprise:

(1) entire chip application scheme (as shown in Figure 4) is to adopt anti-sharp (Flyback) to power up the slow mode of pressing mold, thereby has realized single-level power factor correction, and when the loop operate as normal, the voltage on the COMP Pin pin is stable, as shown in Figure 3, and by:

I ₀×t _on＝C ₄×V _comp

Can release:

$t_{\mathrm{on}}=\frac{{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="HSA00000442116000011.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\&times;V_{\mathrm{comp}}}{I_0}$

Because I ₀And C ₄All be constant value, so work as the opening time t of Power MOS _OnWhen constant, the voltage on the COMP Pin pin also is steady state value.When the change in voltage of COMP Pin pin, corresponding t _OnAlso can change, play time effect of limit LED electric current by feedback;

(2) implementation of quasi-resonance control is by FB sample go the to sample feedback voltage of FB pin pin, this voltage includes the flag information of inductive current when interrupted, when inductive current is interrupted, the drain electrode of power MOS can enter resonance condition, open next switch control cycle by control SR latch at resonance during to trough, the so just approximate soft unlatching that has realized 0 voltage and 0 electric current reduces switching loss, greatly so the system effectiveness of complete machine is improved;

(3) by peak sample module go the to sample peak current information Ipeak of the each switch of CS pin pin, negative terminal by a controlled switch input OTA, this switch is the toff square wave control conducting that is produced by toff sample module, and toff is that each cycle internal inductance electric current drops to 0 duration from peak value.Negative terminal at OTA has a square wave input like this, the high level of square wave is to be determined by Ipeak, square wave is that the time of high level is toff, the input signal of this end of oppisite phase is compared with vref (vref=Iref*R) voltage, ring slowly (finger ring road bandwidth is very low) filtering control by OTA makes the mean value of negative terminal input square wave equal vref, so just the mean value of product in a public cycle frequently with inductance peak value and the time of transmitting energy is fixed as a definite value, this product promptly characterizes the average current of time limit load in the public cycle frequently, stablizes thus and lives time limit LED electric current;

According to Fig. 1 and Fig. 2, can obtain:

${\&Integral;}_0^{T_{\mathrm{AC}}}{I}_{\mathrm{PEAK}}\&times;\frac{T_{\mathrm{OFF}}}{T_S}\mathrm{dt}={\&Integral;}_0^{T_{\mathrm{AC}}}{I}_{\mathrm{REF}}\mathrm{dt}$

$\frac{1}{T_{\mathrm{AC}}}\&times;{\&Integral;}_0^{T_{\mathrm{AC}}}{I}_{\mathrm{PEAK}}\&times;\frac{T_{\mathrm{OFF}}}{T_S}\mathrm{dt}=I_{\mathrm{REF}}\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\left(1\right)$

$I_{\mathrm{OUT}}=\frac{1}{T_{\mathrm{AC}}}\&times;{\&Integral;}_0^{T_{\mathrm{AC}}}\frac{1}{2}\&times;I_{\mathrm{PEAK}}\&times;N\&times;\frac{T_{\mathrm{OFF}}}{T_S}\mathrm{dt}\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\left(2\right)$

According to expression formula (1) and (2):

$I_{\mathrm{OUT}}=\frac{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HSA00000442116000011.png,HSA00000442116000022.png"\; state="\{\{state\}\}">N</figure-callout>}}{2}\&times;I_{\mathrm{REF}}$

(4) because system works in the quasi-resonance control model, during the Cycle by Cycle current limliting, arrives I by the each peak current of comparator _LimitJust close Power MOS during current limliting, just limited maximum intake thus.And when load short circuits; each cycle all can be triggered max power constraint by this comparator in logic module; by the counter in the logic module; behind full n time of continuous counter; thorough shutoff system; no longer,, realize the load short circuits protection thus up to power on next time to any energy of system transmissions.

Description of drawings

A separate AC-DC of Fig. 1 instead swashs the led chip system block diagram, wherein 1---low pressure difference linear voltage regulator, 2---band gap reference, 3---biasing circuit, 4---undervoltage lockout circuit, 5---go up clamp circuit, 6---following clamp circuit, 7---feedback sampling circuit, 8---the peak value sampling circuit, 9---trsanscondutance amplifier, 10FB pin sample circuit, 11---trsanscondutance amplifier, 12---comparator, 13---logical circuit, 14---triangular signal produces circuit, 15---comparator, 16---set-reset flip-floop, 17---drive circuit;

Fig. 2 pin waveform testing figure;

Fig. 3 PFC booster converter associated voltage and current waveform figure, wherein 1---input voltage, 2---inductive current, 3---peak current and electric current envelope ripple, 4---average current-input current;

Fig. 4 chip application circuit diagram;

Fig. 5 chip pin schematic diagram.

Embodiment

Below by embodiment, and in conjunction with the accompanying drawings, the technical solution of the utility model is described in further detail.

AC power AC charges to C2 by diode ballast bridge and big resistance R 1, when the voltage on the C2 (also being the voltage on the VDD Pin) arrives the threshold value of UVLO module among Fig. 1, chip is started working, when GATE Pin output high level, Power MOS opens, the CS place can sample electric current on the NP winding magnetizing inductance of main limit by resistance R cs, FB Pin pin by auxiliary winding NF by the FB sample module of the inside flag information of NP inductive current when interrupted of sampling, can also sample the simultaneously reflected voltage of load place, at the switch of GATE end control Power MOS, realize stablize LED electric current etc. and act on (in conjunction with 2 and 3 description in the last joint).Wherein D1 is unidirectional conducting diode, only opens when energy is transmitted on inferior limit on main limit; D3 is the rectifier diode on time limit; C5 is an output filter capacitor; RFB1, RFB2: divider resistance, the voltage swing of adjusting FB Pin pin; C2, R2 and D2 have constituted the clamp circuit of PowerMOS drain terminal, do not allow powerMOS drain terminal overtension; COMP is OTA output, meets building-out capacitor C4, and whole loop is compensated.

(1). the utility model adopts the control mode of voltage-mode to force down loop bandwidth, the opening time approximately equal of Power MOS in a public cycle frequently, line voltage is high more, corresponding input current is big more, therefore the mean value of input current is identical with the phase place of input voltage, and harmonic distortion is very little, so in stable limit LED electric current, also have very high power factor;

(2). after the release of the energy in the winding of inferior limit finishes, the FB Pin pin voltage that contains the flag information of inductive current when interrupted by packet of samples, the drain-source voltage of judging Power MOS is in valley, at this moment driving Power MOS opens, the result can be that the current spike of conducting will minimize, and opens next switch control cycle by the SR latch because parasitic capacitance is charged to minimum voltage, effectively reduce switching loss, improve overall efficiency;

(3). the electric current on the NP winding magnetizing inductance of main limit is sent into CS Pin pin after being detected by resistance R cs, the ON time by relatively controlling time limit diode D3 and whole switching time ratio constant, thereby the stable time limit LED electric current of living;

(4). when load short circuits, primary and secondary limit peak value can be in cut-off current always, and at this moment system can restart automatically.

Claims (5)

1. a separate AC-DC instead swashs the LED driving power, comprise that AC-DC instead swashs LED chip for driving (1), switching power tube (2), winding magnetizing inductance (3), electric capacity (4), resistance (5) and diode (6), it is characterized in that described AC-DC instead swashs the VDD Pin pin and the electric capacity (4) of LED chip for driving (1), resistance (5) links to each other with diode (6), FB Pin pin links to each other with resistance (5), COMP Pin pin links to each other with electric capacity (4), GATE Pin pin links to each other with switching power tube (2), CS Pin pin and switching power tube (2), resistance (5) links to each other, and GND Pin pin links to each other with resistance (5).

2. instead swash the LED driving power according to claim 1 described separate AC-DC, it is characterized in that: described AC-DC instead swashs LED chip for driving (1), switching power tube (2), winding magnetizing inductance (3), electric capacity (4), resistance (5) and diode (6) and has constituted single-level power factor correction (PFC), only just finished Current Control with the one-level controller, have power simultaneously concurrently and draw calibration function, and power factor has been saved optocoupler and numerous auxiliary element commonly used in traditional inverse-excitation type design more than 98%.

3. instead swash the LED driving power according to claim 1 described separate AC-DC, it is characterized in that: described AC-DC instead swashs LED chip for driving (1), switching power tube (2), winding magnetizing inductance (3), electric capacity (4) and resistance (5) and has constituted quasi-resonance control, has improved overall efficiency.By 0 o'clock, expression this moment, drain terminal voltage entered resonance condition at the electric current that flows through switching power tube (2), then in the lowest point of resonance, open power switch (2), the loss minimum of switch reaches maximum efficient with this so in theory, and overall efficiency reaches as high as more than 90%.

4. instead swash the LED driving power according to claim 1 described separate AC-DC, it is characterized in that: described AC-DC instead swashs the precision control that LED chip for driving (1), switching power tube (2), winding magnetizing inductance (3), electric capacity (4), resistance (5) and diode (6) have constituted LED output constant current.Need not time marginal ray coupling device and constant pressure and flow control circuit, utilize main limit control technology, detect main limit electric current, it is constant to control main limit current peak, and the control switch duty ratio realizes constant pressure and flow output simultaneously, reaches the requirement of isolation simultaneously again.

5. instead swash the LED driving power according to claim 1 described separate AC-DC, it is characterized in that: described AC-DC instead swash LED chip for driving (1) inner integrated maximal input restriction and load short circuit protection function.Cycle by Cycle current limliting by main limit peak value reaches the restriction of maximal input, simultaneously in a limiting time, main limit peak value reaches cut-off current continuously, and represent that load has entered short-circuit condition this moment, and system will enter holding state automatically, after the certain time, system can restart.

Images