CN203968002U - LED self-oscillation drive circuit with output over-voltage protection function - Google Patents

Abstract

The utility model discloses a kind of LED self-oscillation drive circuit with output over-voltage protection function; be mainly used in field and other systems based on self-oscillation work such as AC-DC power supply, LED driving, comprise LED self-maintained circuit, output voltage detecting circuit, output overvoltage protection circuit, peak value current-limiting circuit or door OR1, drive circuit, switch Mdn and resistance R cs.Described LED self-maintained circuit is by triode Qdrv, sustained diode out, the LED laod network being comprised of Cout and LED load and resonance the electric circuit constitute.Described resonant circuit is comprised of transformer T1, resistance R 1 and capacitor C 1.Its advantage is to provide stable output current and realizes output voltage over-voltage protecting function, thereby improves the performance of self-oscillation drive circuit, prevents that output voltage overvoltage from causing damage, improves the reliability of system.

Description

LED self-oscillation drive circuit with output over-voltage protection function

Technical field

The utility model relates to a kind of LED self-oscillation drive circuit, particularly a kind of LED self-oscillation drive circuit with output over-voltage protection function.

Background technology

In LED self-oscillation drive circuit, it is larger that output current is affected by system input supply voltage, and lack the risk that output over-voltage protection function makes circuit exist output capacitance overvoltage to damage.

Fig. 1 is a kind of circuit diagram of traditional LED self-oscillation drive circuit.As shown in Figure 4, the output current Iout of system is:

$\mathrm{Iout}=\frac{\mathrm{Ipk}}{2}---\left(1\right);$

Wherein, Ipk is transformer inductance current peak.

The triode of traditional LED self-oscillation drive circuit is by transformer primary side magnetic saturation Time dependent by the time that is conducting to shutoff, the magnetic saturation resonant inductance current peak Ipk that different system input supply voltage is corresponding different, finally causes different output current Iout.Traditional LED self-oscillation drive circuit output current can change 10%～20% left and right with system input power.On the other hand, owing to lacking corresponding protective circuit, system is easily exported the problem that LED load open circuit causes damage, affects system reliability.

Utility model content

A kind of LED self-oscillation drive circuit with output over-voltage protection function providing of the present utility model, to overcome the defect of above-mentioned prior art.

The utility model provides a kind of LED self-oscillation drive circuit with output over-voltage protection function, comprises LED self-maintained circuit, output voltage detecting circuit, output overvoltage protection circuit, peak value current-limiting circuit or door OR1, drive circuit Gate, switch Mdn, the second resistance R cs; LED self-maintained circuit comprises LED load circuit and resonant circuit; LED load circuit comprises triode Qdrv, sustained diode out, load capacitance Cout and LED diode (LED); Resonant circuit comprises transformer T1, the first resistance R 1 and capacitor C 1; The second resistance R cs detects output current, and output voltage detecting circuit detects output voltage, and switch Mdn turn-offs triode Qdrv; Or door OR1 two inputs be connected with output overvoltage protection circuit, peak value current-limiting circuit respectively, output is connected with drive circuit Gate; Drive circuit Gate is connected with switch Mdn.

Further, the utility model provides a kind of LED self-oscillation drive circuit with output over-voltage protection function, can also have such feature: the second resistance R cs is connected between the emitter Vcs and earth terminal of triode Qdrv.

Further, the utility model provides a kind of LED self-oscillation drive circuit with output over-voltage protection function, peak value current-limiting circuit comprise the first comparator C p1 and One-shot circuit; The first comparator C p1 is voltage Vcs and the first reference voltage V rcs of the second resistance R cs relatively; One-shot circuit produces the pulse signal that turn-offs triode Qdrv.

Further, the utility model provides a kind of LED self-oscillation drive circuit with output over-voltage protection function, can also have such feature: output voltage detecting circuit comprises the 3rd resistance R up and the 4th resistance R dn.

Further, the utility model provides a kind of LED self-oscillation drive circuit with output over-voltage protection function, can also have such feature: output overvoltage protection circuit comprise the circuit that takes absolute value, the second comparator C p2 and latch cicuit; The circuit that takes absolute value changes the voltage Vfb between the 3rd resistance R up and the 4th resistance R dn into positive voltage by negative voltage; The second comparator C p2 relatively take absolute value output voltage V abs and the second reference voltage V rfb of circuit; The output of latch circuit latches the second comparator C p2.

Further, the utility model provides a kind of LED self-oscillation drive circuit with output over-voltage protection function, can also have such feature: switch Mdn can adopt any one in PMOS pipe, NMOS pipe, PNP pipe and NPN pipe.

Further, the utility model provides a kind of LED self-oscillation drive circuit with output over-voltage protection function, can also have such feature: triode Qdrv can adopt metal-oxide-semiconductor.

The beneficial effect of utility model

The utility model provides a kind of LED self-oscillation drive circuit with output over-voltage protection function, when system input power changes, by peak value current-limiting circuit, resonant inductance current peak is remained unchanged, thereby output current is remained unchanged.Check output voltage V out, output voltage V out is too high turn-offs triode Qdrv with the self-oscillation of ends with system by Mdn, thereby realizes output over-voltage protection.The utility model can accomplish that output current can change 5% left and right with system input power, and by output over-voltage protection, prevents that the reasons such as LED load open circuit from causing damage.

The utility model provides a kind of LED self-oscillation drive circuit with output over-voltage protection function; solving traditional LED self-oscillation drive circuit output current changes excessive and lacks the problem that output over-voltage protection function easily causes damage with system input power; thereby improve the performance of self-oscillation drive circuit; prevent that output voltage overvoltage from causing damage, improve the reliability of system.

The utility model provides a kind of LED self-oscillation drive circuit with output over-voltage protection function; be mainly used in the fields such as AC-DC power supply, LED driving and other systems based on self-oscillation work stable output current to be provided and to realize output voltage overvoltage protection; improve the performance of self-oscillation drive circuit; prevent that output voltage overvoltage from causing circuit to damage, and improves the reliability of system.

Accompanying drawing explanation

Fig. 1 is the circuit diagram of traditional LED self-oscillation drive circuit.

Fig. 2 is the block diagram of the LED self-oscillation drive circuit with output over-voltage protection function in the utility model.

Fig. 3 is the circuit diagram of the LED self-oscillation drive circuit with output over-voltage protection function in the utility model.

Fig. 4 is the working waveform figure of traditional LED self-oscillation drive circuit.

Fig. 5 is the working waveform figure with output over-voltage protection function LED self-oscillation drive circuit in the utility model.

Fig. 6 is the working waveform figure with output over-voltage protection function LED self-oscillation drive circuit output over-voltage protection function in the utility model.

Embodiment

Below in conjunction with the drawings and specific embodiments, the utility model is further described.

As shown in Figures 2 and 3, the LED self-oscillation drive circuit with output over-voltage protection function comprises: LED self-maintained circuit, output voltage detecting circuit, output overvoltage protection circuit, peak value current-limiting circuit or door OR1, drive circuit Gate, switch Mdn, the second resistance R cs.

LED self-maintained circuit comprises LED load circuit and resonant circuit.

LED load circuit comprises triode Qdrv, sustained diode out, load capacitance Cout and LED diode (LED).

Resonant circuit comprises transformer T1, the first resistance R 1 and capacitor C 1.

The two ends of transformer T1 mono-side are connected with collector electrode, the LED diode cathode of triode Qdrv respectively.The two ends of transformer T1 opposite side are connected with emitter, the capacitor C 1 of triode Qdrv respectively; Also be connected with the two ends of output voltage detecting circuit.Triode Qdrv can adopt metal-oxide-semiconductor.

The other end of capacitor C 1 is connected with the first resistance R 1.The other end of the first resistance is connected with the base stage of triode Qdrv.

The positive pole of sustained diode out is connected with the collector electrode of triode Qdrv, and negative pole is connected with the positive pole of LED diode.Load capacitance Cout is in parallel with LED diode (LED).

Switch Mdn can adopt PMOS pipe, NMOS pipe, PNP pipe and NPN pipe.The drain electrode of switch Mdn is connected with the base stage of triode Qdrv, and grid is connected with drive circuit, and source electrode is connected with earth terminal.

The second resistance R cs is connected between the emitter Vcs and earth terminal of triode Qdrv.The second resistance R cs detects output current, and output voltage detecting circuit detects output voltage, and switch Mdn turn-offs triode Qdrv.

Or door OR1 two inputs be connected with output overvoltage protection circuit, peak value current-limiting circuit respectively, output is connected with drive circuit Gate.

Output voltage detecting circuit comprises the 3rd resistance R up and the 4th resistance R dn.

Peak value current-limiting circuit comprise the first comparator C p1 and One-shot circuit.The first comparator C p1 is voltage Vcs and the first reference voltage V rcs of the second resistance R cs relatively.One-shot circuit produces the pulse signal that turn-offs triode Qdrv.

Output overvoltage protection circuit comprise the circuit that takes absolute value, the second comparator C p2 and latch cicuit.The circuit that takes absolute value changes the voltage Vfb between the 3rd resistance R up and the 4th resistance R dn into positive voltage by negative voltage.The second comparator C p2 relatively take absolute value output voltage V abs and the second reference voltage V rfb of circuit.The output of latch circuit latches the second comparator C p2.

As shown in Figure 4, by peak value current-limiting circuit control transformer inductive current peak, Ipk does not change with system input voltage, thus stabilizing output current.By output voltage detecting circuit, detect output voltage size, when there is output overvoltage, make Mdn conducting, turn-off triode Qdrv with the self-oscillation of ends with system, thereby realize output over-voltage protection.

The specific works principle of the LED self-oscillation drive circuit with output over-voltage protection function is as shown in Figure 3:

As shown in Figure 5, after triode Qdrv conducting, transformer inductance electric current raises gradually from 0A, resistance R cs detects the size of transformer inductance electric current, when transformer inductance electric current increases to the peak current of peak value current-limiting circuit setting, amplifier Cp1 exports high level, triggers One-shot circuit and produces a high level pulse, and process or door OR1 and drive current make Mdn conducting turn-off triode Qdrv.The transformer inductance peak current that peak value current-limiting circuit is set is:

$\mathrm{Ipk}=\frac{\mathrm{Vrcs}}{\mathrm{Rcs}}---\left(2\right);$

Triode Qdrv closes and has no progeny, and transformer inductance electric current reduces gradually from Ipk, and when transformer inductance electric current will reach after 0A, LED self-maintained circuit makes triode Qdrv conducting again by transformer TI, capacitor C 1 and resistance R 1.

By resistance R cs, carry out the output current of initialization system, size is:

$\mathrm{Iout}=\frac{\mathrm{Ipk}+0A}{2}=\frac{1}{2}\×\frac{\mathrm{Vrcs}}{\mathrm{Rcs}}---\left(3\right);$

The specific works principle that the LED self-oscillation drive circuit with output over-voltage protection function is as shown in Figure 3 realized output over-voltage protection is:

As shown in Figure 6, when triode Qdrv turn-offs, the original edge voltage of transformer T1 equals output voltage V out, and the output voltage V fb of output voltage detecting circuit is:

$\mathrm{Vfb}=-\frac{\mathrm{Vout}}{\mathrm{Kpa}}\×\mathrm{Kfb}---\left(4\right);$

Wherein, Kpa is transformer primary side and auxiliary limit turn ratio.

$\mathrm{Kfb}=-\frac{\mathrm{Rdn}}{\mathrm{Rup}+\mathrm{Rdn}}---\left(5\right);$

Vfb voltage changes positive voltage Vabs and reference voltage V rfb comparison into through the circuit that takes absolute value.The too high Vabs of causing of output voltage V out is greater than reference voltage V rfb; comparator C p2 exports high level, and latch circuit latches high level produces OVP high level, and warp or door OR1 and drive circuit make Mdn conducting turn-off triode Qdrv; thereby system is quit work, realize defencive function.Output overvoltage voltage Vout_ovp can arrange by revising the proportionate relationship Kfb of resistance R up and resistance R dn, and output overvoltage voltage Vout_ovp is:

$\mathrm{Vout}\_\mathrm{ovp}=\frac{\mathrm{Vrfb}}{\mathrm{Kfb}}\×\mathrm{Kpa}---\left(6\right);$

Although content of the present utility model has been done detailed introduction by above preferred embodiment, will be appreciated that above-mentioned description should not be considered to restriction of the present utility model.Those skilled in the art, read after foregoing, for multiple modification of the present utility model with to substitute will be all apparent.Any utility model that does not exceed the utility model connotation scope is created; include but not limited to resistance implementation as Rcs adopt the change of conventional, electric-resistance or MOS resistance etc., to the replacement of the type of components and parts or model if the change that Mdn is replaced to triode etc., circuit local structure is as increased line voltage compensation circuit etc.; and the replacement of other unsubstantialities, distortion or modification, within all falling into the utility model protection range.

Claims (7)

1. with a LED self-oscillation drive circuit for output over-voltage protection function, it is characterized in that:

Comprise LED self-maintained circuit, output voltage detecting circuit, output overvoltage protection circuit, peak value current-limiting circuit or door (OR1), drive circuit (Gate), switch (Mdn), the second resistance (Rcs);

Wherein, described LED self-maintained circuit comprises LED load circuit and resonant circuit;

Described LED load circuit comprises triode (Qdrv), fly-wheel diode (Dout), load capacitance (Cout) and LED diode (LED);

Described resonant circuit comprises transformer (T1), the first resistance (R1) and electric capacity (C1);

Described the second resistance (Rcs) detects output current, and described output voltage detecting circuit detects output voltage, and described switch (Mdn) turn-offs described triode (Qdrv);

Two inputs described or door (OR1) are connected with described output overvoltage protection circuit, described peak value current-limiting circuit respectively, and output is connected with described drive circuit (Gate);

Described drive circuit (Gate) is connected with described switch (Mdn).

2. the LED self-oscillation drive circuit with output over-voltage protection function according to claim 1, is characterized in that:

Wherein, described the second resistance (Rcs) is connected between the emitter (Vcs) and earth terminal of described triode (Qdrv).

3. the LED self-oscillation drive circuit with output over-voltage protection function according to claim 2, is characterized in that:

Wherein, described peak value current-limiting circuit comprises the first comparator (Cp1) and One-shot circuit;

The voltage (Vcs) of more described the second resistance of described the first comparator (Cp1) (Rcs) and the first reference voltage (Vrcs);

Described One-shot circuit produces the pulse signal that turn-offs described triode (Qdrv).

4. the LED self-oscillation drive circuit with output over-voltage protection function according to claim 1, is characterized in that:

Wherein, described output voltage detecting circuit comprises the 3rd resistance (Rup) and the 4th resistance (Rdn).

5. the LED self-oscillation drive circuit with output over-voltage protection function according to claim 4, is characterized in that:

Wherein, described output overvoltage protection circuit comprises the circuit that takes absolute value, the second comparator (Cp2) and latch cicuit;

The described circuit that takes absolute value changes the voltage (Vfb) between described the 3rd resistance (Rup) and described the 4th resistance (Rdn) into positive voltage by negative voltage;

Described the second comparator (Cp2) relatively take absolute value output voltage (Vabs) and the second reference voltage V rfb of circuit;

The output of the second comparator (Cp2) described in described latch circuit latches.

6. the LED self-oscillation drive circuit with output over-voltage protection function according to claim 1, is characterized in that:

Wherein, described switch (Mdn) can adopt any one in PMOS pipe, NMOS pipe, PNP pipe and NPN pipe.

7. the LED self-oscillation drive circuit with output over-voltage protection function according to claim 1, is characterized in that:

Wherein, described triode (Qdrv) can adopt metal-oxide-semiconductor.