CN219351947U

CN219351947U - LED lamp and LED driving circuit

Info

Publication number: CN219351947U
Application number: CN202223607673.2U
Authority: CN
Inventors: 王宗友; 李明峰
Original assignee: Guangdong Songsheng Power Technology Co ltd
Current assignee: Guangdong Songsheng Power Technology Co ltd
Priority date: 2022-12-30
Filing date: 2022-12-30
Publication date: 2023-07-14
Anticipated expiration: 2032-12-30

Abstract

The utility model discloses an LED lamp and an LED driving circuit, wherein the LED driving circuit comprises a constant current module for outputting constant current to an LED load, and a current ripple suppression module for suppressing ripple of the load current, and further comprises: an inductance connected in series in the load loop and adapted to resist abrupt changes in the load current when a load short circuit occurs. By implementing the technical scheme of the utility model, the inductance is introduced into the LED drive circuit, so that the reliability of short-circuit protection is improved, the whole current ripple suppression module cannot fail due to load short circuit, and the introduced inductance can be selected from inductances with smaller inductance and volume, so that the cost and the volume are saved.

Description

LED lamp and LED driving circuit

Technical Field

The utility model relates to the field of power supplies, in particular to an LED lamp and an LED driving circuit.

Background

At present, the traditional LED driving circuit in the market is a two-stage structure of PFC module and switch DC/DC module, while the common isolated LED driving circuit can be a structure of PFC module and QR flyback module, a structure of PFC module and LLC module, and the non-isolated LED driving circuit can be a structure of PFC module and BUCK module.

A new scheme of LED driving circuit recently developed is: the constant current PFC module and the current ripple suppression module are characterized in that the first-stage PFC module is constant current output and can directly drive an LED load, but obvious stroboscopic effect exists due to larger power frequency ripple caused by AC, so that the current ripple suppression module is additionally arranged behind the constant current PFC module and is used for suppressing the power frequency ripple, and the current for finally driving the LED load meets the requirement of the stroboscopic coefficient. The LED driving scheme has great advantages in cost, volume and performance of EMI compared with the traditional two-stage LED driving scheme because one-stage switch type DC/DC module is omitted and one large magnetic element and a freewheeling diode are omitted on the device. However, the current ripple suppression module cannot truly achieve the short-circuit protection without failure even if the current ripple suppression module itself has the function of short-circuit protection due to the circuit structure thereof.

For example, in the LED driving circuit shown in fig. 1, when a load short circuit occurs between led+, LED-, the following voltage relationship exists: v (CE 1) =V (Q1_DS) +V (RS 1), because the voltage of the capacitor CE1 cannot be suddenly changed, the short-circuit instant voltage V (CE 1) can form a series voltage division relation with the detection resistor RS1 through the drain-source resistor R (DS_ON) of the MOS tube Q1, so that the MOS tube Q1 can bear one energy P (Q1), and the detection resistor RS1 can also bear one energy P (Q1)P (RS 1), wherein P (Q1) =v (q1_ds) ² /R(DS_ON)，P(RS1)＝V(RS1) ² The energy of R (RS 1) is sufficient to cause the MOS transistor Q1 and the detection resistor RS1 to fail instantaneously at the moment of short circuit. Further, the higher the voltage of the capacitor CE1, the worse the case, and the greater the probability of failure. Meanwhile, the voltage withstand value of the current detecting pin CS of the control chip U1 is also exceeded by the higher V (RS 1), causing damage to the control chip U1. Although the CS pin of the control chip U1 and the DET script body have the functions of short-circuit identification and performing corresponding protection actions, the MOS transistor Q1, the resistor R1 and the control chip U1 have failed in the period from the time when the load short-circuit occurs to the time when the load short-circuit is identified to the time when the load short-circuit is performed and then the load short-circuit is performed, so that the short-circuit protection function of the current ripple suppression module is difficult to truly perform the function of short-circuit protection.

Disclosure of Invention

The utility model aims to solve the technical problem that short-circuit protection can fail in the prior art, and provides an LED lamp and an LED driving circuit.

The technical scheme adopted for solving the technical problems is as follows: an LED driving circuit is constructed including a constant current module for outputting a constant current to an LED load, and a current ripple suppression module for ripple suppressing a load current, further comprising:

an inductance connected in series in the load loop and adapted to resist abrupt changes in the load current when a load short circuit occurs.

Preferably, the inductor is an I-shaped inductor or a toroidal inductor.

Preferably, the constant current module includes:

a PFC constant current unit for outputting constant current; and

and the electrolytic capacitor is connected between the positive output end of the PFC constant current unit and the ground.

Preferably, the current ripple suppression module includes:

the switching tube and the detection resistor are connected in series in the load loop; the method comprises the steps of,

and the control unit is used for controlling the conduction degree of the switching tube according to the voltage of the detection resistor so that the voltage at two ends of the switching tube follows the voltage of the electrolytic capacitor.

Preferably, the control unit is a control chip with model numbers of JW1221, KP421 and MT 7636.

Preferably, the positive output end of the constant current module is connected with the positive end of the LED load, the negative end of the LED load is connected with the first end of the inductor, the second end of the inductor is connected with the first end of the switching tube, the second end of the switching tube is connected with the first end of the detection resistor, the second end of the detection resistor and the negative output end of the constant current module are respectively grounded, the first end of the detection resistor is also connected with the current detection end of the control chip, and the control end of the control chip is connected with the control end of the switching tube.

Preferably, the current ripple suppression module further includes a first voltage dividing resistor and a second voltage dividing resistor, wherein a first end of the first voltage dividing resistor is connected to a second end of the inductor, a second end of the first voltage dividing resistor is respectively connected to a voltage detection end of the control chip and a first end of the second voltage dividing resistor, and a second end of the second voltage dividing resistor is grounded.

Preferably, the current ripple suppression module further comprises a current limiting resistor connected between the control end of the control chip and the control end of the switching tube.

Preferably, the current ripple suppression module further comprises an isolation resistor connected between the control terminal of the switching tube and ground.

The utility model also constructs an LED lamp, which comprises an LED load and the LED driving circuit.

By implementing the technical scheme of the utility model, the inductance is introduced into the LED drive circuit, and the inductance has the characteristic that the current cannot be suddenly changed, so that the sudden change of the load current can be resisted when a load circuit occurs, the reliability of short circuit protection is improved, and the whole current ripple suppression module cannot be disabled due to load short circuit. In addition, compared with the inductance in the BUCK module, the inductance in the technical scheme can be smaller in inductance and volume, and cost and volume are saved.

Drawings

The utility model will be further described with reference to the accompanying drawings and examples, in which:

fig. 1 is a circuit diagram of a conventional LED driving circuit;

FIG. 2 is a logic block diagram of a first embodiment of an LED lamp of the present utility model;

fig. 3 is a circuit diagram of a first embodiment of the LED driving circuit of the present utility model.

Detailed Description

The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

Fig. 2 is a logic structure diagram of a first embodiment of the LED lamp according to the present utility model, where the LED lamp of the embodiment includes an LED load 20 and an LED driving circuit 10 for driving the LED load 20, where the LED driving circuit 10 includes a constant current module 11, a current ripple suppression module 12, and an inductance L1, and the constant current module 11 is configured to output a constant current to the LED load 20; the current ripple suppression module 12 is used for carrying out ripple suppression on load current; the inductor L1 is connected in series in the load loop, and is used for resisting abrupt change of load current when load short circuit occurs, wherein the inductor L1 can be an i-shaped inductor, a toroidal inductor, or other types of differential mode inductors.

In this embodiment, since the inductor L1 is introduced into the LED driving circuit, and the inductor L1 has a characteristic that the current does not suddenly change, the sudden change of the load current can be resisted when the load circuit occurs, the reliability of the short-circuit protection is increased, and the whole current ripple suppression module does not fail due to the load short circuit. In addition, it should be noted that, although the inductance also exists in the conventional BUCK module, the inductance in this embodiment is smaller than the inductance in the BUCK module, and the inductance with smaller inductance and smaller volume can be selected, and the specific analysis is as follows:

in a conventional BUCK module, an MOS tube is in a switching state (saturation and cut-off alternating state), so that an inductor in the BUCK module stores energy in the saturation state of the MOS tube, and energy is discharged when the MOS tube is cut-off, namely, the energy transmitted on the inductor is as much as the energy consumed by an LED load, so that peak current on the inductor is relatively large, the requirement of energy transmission can be met by a certain amount of inductance and a certain magnetic core volume, and the magnetic core cannot reach the saturation state;

in the technical solution of this embodiment, it is only necessary to ensure that the inductance L1 is not saturated in the period from the start of the load short circuit to the short-circuit protection by the current ripple suppression module, and the period from the start of the load short circuit to the short-circuit protection by the current ripple suppression module is very short and not more than 100ns, and the turn-on time of the switching tube is much smaller than that of the bus module, so that the inductance L1 of this embodiment is much smaller than that of the inductance in the existing bus module.

Fig. 3 is a circuit diagram of a first embodiment of the LED driving circuit according to the present utility model, where the LED driving circuit includes a constant current module, a current ripple suppression module, and an inductance L1, and the constant current module is configured to output a constant current to an LED load; the current ripple suppression module is used for carrying out ripple suppression on load current; an inductance L1 is connected in series in the load loop and is used to resist abrupt changes in the load current when a load short circuit occurs.

In a constant current module, comprising: the PFC constant current unit U2 and the electrolytic capacitor CE1, wherein the PFC constant current unit U2 is used for outputting constant current; the electrolytic capacitor CE1 is connected between the positive output end of the PFC constant current unit U2 and the ground, is a large capacitor, and is used for storing energy transferred by the PFC constant current unit U2 and is used for being transmitted to an LED load.

In a current ripple suppression module, comprising: the switching tube Q1, the detection resistor RS1 and the control unit, and in this embodiment, the detection resistor RS1 is used for detecting the load current in real time and has an overcurrent protection function. The control unit is a control chip U1 for controlling the conduction degree of the switching tube Q1 according to the voltage of the detection resistor RS1, namely, controlling the drain-source voltage of the switching tube Q1, so that the voltage at two ends of the switching tube Q1 follows the voltage of the electrolytic capacitor CE1, and reducing the alternating voltage component between the LEDs+ and the LEDs- (on the LED load) as much as possible. The control chip U1 may be, for example, a control chip with model numbers JW1221, KP421, MT7636, but in other embodiments, may be composed of a plurality of discrete components and have the same functions as the control chip U1. The switching tube Q1 is a MOS tube, but of course, in other embodiments, it can be another type of switching tube. In addition, in this embodiment, the switching tube Q1 and the detection resistor RS1 are connected in series in the load loop, that is, the positive output end of the PFC constant current unit U2 is connected to the positive end (led+), the negative end (LED-) of the LED load is connected to the first end of the inductor L1, the second end of the inductor L1 is connected to the first end (drain) of the switching tube Q1, the second end (source) of the switching tube Q1 is connected to the first end of the detection resistor RS1, and the second end of the detection resistor RS1 and the negative output end of the PFC constant current unit U2 are grounded. The first end of the detection resistor RS1 is further connected to a current detection end (CS) of the control chip U1, and a control end (GATE) of the control chip U1 is connected to a control end (GATE) of the switching tube Q1.

In addition, the current ripple suppression module further includes a first voltage dividing resistor R1, a second voltage dividing resistor R2, a current limiting resistor R3, and an isolation resistor R4, wherein a first end of the first voltage dividing resistor R1 is connected to a second end of the inductor L1, a second end of the first voltage dividing resistor R1 is respectively connected to a voltage Detection End (DET) of the control chip U1 and a first end of the second voltage dividing resistor R2, a second end of the second voltage dividing resistor R2 is grounded, and the first voltage dividing resistor R1 and the second voltage dividing resistor R2 are used for detecting a drain voltage of the switching tube Q1 and transmitting the drain voltage to the control chip U1 for short circuit identification. The current limiting resistor R3 is connected between the control end of the control chip U1 and the control end of the switching tube Q1. The isolation resistor R4 is connected between the control terminal of the switching tube Q1 and ground.

In this embodiment, when operating normally (no short circuit fault occurs), the PFC constant current unit U2 generates a relatively stable dc current, and a voltage ripple of 2 times the power frequency sine wave profile is generated on the capacitor CE 1. The control chip U1 controls the switching tube Q1 to operate in a linear section, so that the voltage between the drain and the source follows the voltage ripple on the capacitor CE1, so that the voltage (load voltage) between the leds+ and the LED-is relatively stable, the voltage ripple is as small as possible, and the ripple of the load current is suppressed to a certain extent. Meanwhile, the detection resistor RS1 is used for sampling the magnitude of the load current in real time and transmitting the load current to the current detection end CS of the control chip U1, and the voltage dividing resistors R1 and R2 are used for sampling the drain voltage of the switching tube Q1 in real time and transmitting the drain voltage to the voltage detection end DET of the control chip U1.

When a short circuit fault occurs, the load current will not be suddenly changed due to the existence of the inductor L1, the voltage of the capacitor CE1 will be initially and fully loaded at two ends of the inductor L1, the current of the inductor L1 will linearly increase in the form of Δi, where Δi=v (CE 1) ×t/L ₁ V (CE 1) is the voltage of the capacitor CE1, L ₁ The inductance value of the inductor L1 is i=io+Δi, and Io is the load current during normal operation. In this stage, as long as T is short enough, the inductor L1 will not saturate, and the limited current will not cause the failure of the switching tube Q1 and the detection resistor RS1, so it is only necessary to ensure that the inductor L1 does not saturate during the time delay from the start of the load short circuit to the identification of the short circuit state by the control chip U1 and the provision of the turn-off signal to the switching tube Q1, and the whole current ripple suppression module is safe, i.e. the short circuit protection function of the current ripple suppression module is effective. Here, the time when the load is short-circuited (the time when the signals of the current detection terminal and the voltage detection terminal are transmitted to the control chip U1) is defined as Td1, the time when the control chip U1 transmits the turn-off signal to the switching transistor Q1 is defined as Td2, and then the current I (L1) on the inductor L1 after the short circuit and the current passing through the switching transistor Q1 satisfy the formula: i (L1) =io+v (CE 1) × (td1+td2)/L ₁ . In addition, since Td1 and Td2 are nanosecond signals and do not exceed 100ns after addition, compared with the existing BUCK module in which the switching tube has a switching time of most us, the minimum time for the inductor L1 to reach unsaturation is smaller in the embodiment, the required inductance and the magnetic core volume are small, and therefore the addition of the inductor L1 does not inhibit the current rippleThe modules bring about an increase in cost and an increase in power supply size.

The above description is only of the preferred embodiments of the present utility model and is not intended to limit the present utility model, but various modifications and variations can be made to the present utility model by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model should be included in the scope of the claims of the present utility model.

Claims

1. An LED driving circuit including a constant current module for outputting a constant current to an LED load, and a current ripple suppression module for ripple suppressing a load current, characterized by further comprising:

2. The LED driving circuit of claim 1, wherein the inductor is an i-inductor, a toroidal inductor.

3. The LED driving circuit according to claim 1, wherein the constant current module includes:

a PFC constant current unit for outputting constant current; and

4. The LED driving circuit of claim 3, wherein the current ripple suppression module comprises:

5. The LED driving circuit of claim 4, wherein the control unit is a control chip of model JW1221, KP421, MT 7636.

6. The LED driving circuit of claim 5, wherein the positive output terminal of the constant current module is connected to the positive terminal of the LED load, the negative terminal of the LED load is connected to the first terminal of the inductor, the second terminal of the inductor is connected to the first terminal of the switching tube, the second terminal of the switching tube is connected to the first terminal of the detection resistor, the second terminal of the detection resistor and the negative output terminal of the constant current module are respectively grounded, the first terminal of the detection resistor is further connected to the current detection terminal of the control chip, and the control terminal of the control chip is connected to the control terminal of the switching tube.

7. The LED driving circuit of claim 6, wherein the current ripple rejection module further comprises a first voltage divider resistor and a second voltage divider resistor, wherein a first end of the first voltage divider resistor is connected to a second end of the inductor, a second end of the first voltage divider resistor is connected to the voltage detection end of the control chip and the first end of the second voltage divider resistor, respectively, and a second end of the second voltage divider resistor is grounded.

8. The LED driving circuit of claim 6, wherein the current ripple suppression module further comprises a current limiting resistor connected between the control terminal of the control chip and the control terminal of the switching tube.

9. The LED driving circuit of claim 6, wherein the current ripple suppression module further comprises an isolation resistor connected between the control terminal of the switching tube and ground.

10. An LED luminaire comprising an LED load, characterized in that it further comprises an LED driving circuit as claimed in any one of claims 1-9.