TW201422052A - Protection circuit for light module and electronic device - Google Patents

Abstract

A protection circuit for protecting a light module is provided. The light module includes at least two light components, and a PWM control chip, a bridge rectifier and at least a couple of transformers for driving the at least two light components. The protection circuit includes a comparison circuit and an adjustment trigger circuit. The comparison circuit is connected to a connection node of primary coils of the couple of transformers, and is used to detect a voltage of the connection node and obtain a detection voltage. The comparison circuit is also used to compare the detection voltage with a reference voltage, and output a detection signal when comparing the detection voltage is greater than the reference voltage. The adjustment trigger circuit triggers the PWM control chip to decrease a duty cycle of the PWM signals, when receiving the detection signal.

Description

Light-emitting module protection circuit and electronic device

The present invention relates to a protection circuit, and more particularly to an illumination module protection circuit and an electronic device having the same.

At present, the illumination device and the backlight/light-emitting module of the electronic device usually include a light-emitting element such as an LED (light-emitting diode) or a cold cathode lamp and a corresponding driving circuit. As shown in FIG. 1 , the current lighting module 200 generally includes a PWM voltage signal generated by a PWM (pulse width modulation) control chip 210, a bridge switching circuit 220, and at least one pair of transformers VF to drive the light emitting element to emit light. Specifically, the PWM voltage signal generated by the PWM control chip 210 is converted into a PWM voltage signal in an AC form by the bridge switching circuit 220. The 1 push 1 transformer composed of the at least one pair of transformers VF converts the voltage of the PWM voltage signal in the form of an alternating current into a voltage of an appropriate magnitude and then drives the series of light emitting elements L connected to each pair of transformers VF. The primary coils FC of the pair of transformers VF are connected in series to the two output terminals OT1 and OT2 of the bridge switching circuit 220, and one end of the secondary coil SC of each transformer VF is grounded, and the secondary coil of each transformer VF is connected. The ungrounded terminals are connected to a light-emitting element L, and the two light-emitting elements L are connected to each other such that the two light-emitting elements L are connected in series between the ungrounded terminals of the secondary coils SC of the two transformers VF. In the prior art, in order to prevent a voltage abnormality caused by the absence of illumination of at least one of the light-emitting elements L, such as an increase in damage to the transformer, it is usually between the non-ground terminal of the secondary coil SC of each transformer VF and the ground. Connected to a high voltage capacitor C. When a certain light-emitting element L is not lit, the voltage of the high-voltage capacitor connected to the secondary coil SC where the light-emitting element L is located rises. The PWM control chip prestores a safe voltage value. When comparing the voltage of the high voltage capacitor to exceed the safe voltage, the control reduces the duty ratio of the output PWM voltage signal, reduces the output voltage, thereby avoiding damage to the transformer or the light emitting component. .

However, existing high voltage capacitors are generally expensive.

In view of the above, a light-emitting module protection circuit is provided, which can protect the light-emitting module at a simple price and at a low cost. In addition, the present invention also provides an electronic device having the illumination module protection circuit.

A light-emitting module protection circuit for protecting a light-emitting module, comprising: a PWM control chip, a bridge switching circuit, at least one pair of transformers, and driving through the PWM control chip, the bridge switching circuit and at least one pair of transformers At least two light emitting elements, wherein the protection circuit includes a comparison circuit and an adjustment trigger circuit. The comparison circuit is connected to the primary coil connection node of the at least one pair of transformers for detecting a voltage of the primary coil connection node of the at least one pair of transformers to obtain a detection voltage, and the detection voltage and a reference voltage value For comparison, a detection signal is output when the detection voltage is greater than the reference voltage value. The adjustment trigger circuit is connected to the comparison circuit and the PWM control chip, and is configured to output a trigger voltage to the PWM control chip when the detection signal is received, and trigger the PWM control chip to lower the output PWM voltage signal. Duty cycle.

An electronic device includes a power interface, a light emitting module, and a light emitting module protection circuit, wherein the power interface is configured to provide a DC voltage, and the light emitting module includes a PWM control chip, a bridge switching circuit, at least one pair of transformers, and at least two a light-emitting element, the PWM control chip includes an input end, a controlled end, and an output end, the PWM control chip is connected to the power supply interface through an input end, and receives a power supply voltage of the power supply interface to generate a PWM voltage signal through the output end Output, the bridge switching circuit includes an input end and two output ends, the input end of the bridge switching circuit is connected to an output end of the PWM control chip, and the bridge switching circuit is used to output PWM voltage of the PWM control chip Converting the signal into an AC PWM voltage signal and outputting through the two output terminals; at least one pair of transformers are respectively connected between the two output ends of the bridge switching circuit and the at least two light emitting elements for outputting the bridge switching circuit The alternating PWM voltage signal is converted into a voltage signal of a suitable magnitude to drive the light emitting element to emit light. The illumination module protection circuit includes a comparison circuit and an adjustment trigger circuit. The comparison circuit is connected to the primary coil connection node of the at least one pair of transformers for detecting a voltage of the primary coil connection node of the at least one pair of transformers to obtain a detection voltage, and the detection voltage and a reference voltage value For comparison, a detection signal is output when the detection voltage is greater than the reference voltage value. The adjustment trigger circuit is connected to the comparison circuit and the controlled end of the PWM control chip, and is configured to output a trigger voltage to the controlled end of the PWM control chip when the detection signal is received, triggering the PWM control chip Decrease the duty cycle of the output PWM voltage signal.

The light-emitting module protection circuit of the invention and the electronic device having the protection circuit have the advantages of simple structure and low cost. By detecting the voltage of the connection node of each pair of transformer primary coils, it can be determined whether or not the light-emitting elements are abnormal, and the PWM is correspondingly reduced. The duty cycle of the PWM voltage signal output by the wafer is controlled to protect the transformer or the light-emitting element.

2 is a circuit block diagram of an electronic device 1 having a light-emitting module protection circuit 100 (hereinafter referred to as a protection circuit 100) according to an embodiment of the present invention. The electronic device 1 includes a protection circuit 100, a power interface 300, a PWM (pulse width modulation) control chip 210, a bridge switching circuit 220, at least one pair/two transformers VF1, VF2, and at least two light emitting elements L.

The power interface 300 is used to provide a DC voltage. The PWM control chip 210 includes an input terminal IN, a controlled terminal CP, and an output terminal OT. The PWM control chip 210 is connected to the power supply interface 300 through the input terminal IN, and receives the power supply voltage of the power supply interface 300 to generate a PWM voltage signal to be output through the output terminal OT. The bridge switching circuit 220 includes an input terminal IN1 and two output terminals OT1 and OT2 and the PWM control chip. The input terminal IN1 is connected to the output terminal OT of the PWM control chip 210. The bridge switching circuit 220 controls the PWM control chip 210. The output PWM voltage signal is converted into an AC PWM voltage signal. The at least one pair of transformers VF1 and VF2 are respectively connected between the output terminals OT1 and OT2 of the bridge switching circuit 220 and the at least two light emitting elements L for converting the AC PWM voltage signal of the output of the bridge switching circuit 220 into A light signal of a suitable size drives the light-emitting element L to emit light. The at least one pair of transformers VF1 and VF2 constitute a push-to-transformer pair. In the present embodiment, the power supply interface 300 outputs a DC voltage, for example, a DC voltage of 24V. The power interface can be connected to the power management module of the electronic device 1 to obtain the DC voltage or connected to the battery to obtain the DC voltage.

The primary coil FC1 of the transformer VF1 and the primary coil FC2 of the transformer VF2 are connected in series between the two output terminals OT1, OT2 of the bridge switching circuit 220. The secondary coil SC1 of the transformer VF1 and the secondary coil SC2 of the transformer VF2 each have one end grounded, and the at least two light emitting elements L are connected in series to the ungrounded terminal of the secondary coil SC1 of the transformer VF1 and the secondary coil SC2 of the transformer VF2. between.

As shown in FIG. 2, in the present invention, the protection circuit 100 is connected between the primary coil connection point of the at least one pair of transformers VF1, VF2 and the PWM control wafer 210. The comparison circuit 100 includes a comparison circuit 10 and an adjustment trigger circuit 20. The comparison circuit 10 is connected between the adjustment trigger circuit 20 and the primary coil connection node N of the at least one pair of transformers VF1, VF2, and the adjustment trigger circuit 20 is also connected to the PWM control wafer 210. The comparison circuit 10 is configured to detect a voltage of the primary coil connection node N of the at least one pair of transformers VF1, VF2 to obtain a detection voltage, and compare the detection voltage with a reference voltage value, when comparing the detection When the voltage is greater than the reference voltage value, a detection signal is generated to the adjustment trigger circuit 20. The adjustment trigger circuit 20 receives the detection signal and outputs a trigger voltage higher than the safe voltage value to the PWM control chip 210. After receiving the trigger voltage, the PWM control chip 210 compares the trigger voltage to a safe voltage value stored by the PWM control chip 210, and controls to lower the duty ratio of the output PWM voltage signal, thereby lowering the PWM voltage signal. Voltage. Specifically, in the present invention, the PWM control chip 210 directly controls to adjust the duty ratio of the PWM voltage signal to a predetermined range.

Referring to FIG. 3 together, when the at least two light-emitting elements L are normally illuminated, the load values of the at least two transformers VF1 and VF2 are equal, and the voltage of the PWM voltage signal is set to 24 V (volts), thereby connecting the nodes. The voltage of N is half of the voltage of the PWM voltage signal as shown in Fig. 3a, that is, 12V. When one light-emitting element L is turned off, for example, the light-emitting element L is damaged or not, the load values of the two transformers VF1, VF2 are not equal. Since the PWM voltage signal outputted by the PWM control chip 210 is an AC signal, it is alternately outputted from the output terminals OT1 and OT2, so that the voltage of the connection node N alternates between being higher than the 12V and lower than the 12V, for example, as shown in FIG. 3b. The shown is alternated between 16V and 10V. In this embodiment, the reference voltage value is set to 14V, so that when the light-emitting elements L are all normally operating, the comparison circuit 10 compares the detection voltage to be lower than the reference voltage value, when one of the light-emitting elements L is turned off. The comparison circuit 10 will compare the detected voltage above the reference voltage value to generate the detection signal at a certain time.

4 is a circuit diagram of the electronic device 1 in the first embodiment of the present invention. In the present embodiment, the comparison circuit 10 includes a comparator 101 that includes a non-inverting input (not labeled) and an inverting input (not labeled). The inverting input is coupled to a reference voltage point Vref, which is used to provide the reference voltage value. The non-inverting input is coupled to the primary coil connection node N of the at least two transformers VF1 and VF2. As described above, the reference voltage value of the reference voltage point Vref is set to be slightly higher than half of the voltage value of the PWM voltage signal, and smaller than a larger value of the voltage of the connection node N when a light-emitting element L is abnormal.

The adjustment trigger circuit 20 includes an NMOS transistor Q1 and a resistor R1. The NMOS transistor Q1 and the resistor R1 are connected in series between a voltage terminal Vad and ground. The gate of the NMOS transistor Q1 is connected to the output end of the comparator 101 (not labeled), the source of the NMOS transistor Q1 is connected to the voltage terminal Vad, and the drain of the NMOS transistor Q1 and the resistor R1 are connected. connection. A connection point (not labeled) of the NMOS transistor Q1 and the resistor R1 is connected to the controlled terminal CP of the PWM control wafer 210. The voltage terminal Vad is used to provide the trigger voltage, and the trigger voltage is greater than or equal to a pre-stored safe voltage value in the PWM control chip 210. Obviously, the size of the voltage terminal Vad can be adjusted according to the pre-stored safe voltage value in the PWM control chip 210.

When the comparator 101 compares the detection voltage to be greater than the reference voltage value, a high level signal is output to the gate of the NMOS transistor Q1, thereby turning on the NMOS transistor Q1. Thus, the voltage terminal Vad provides the trigger voltage to the controlled terminal CP of the PWM control wafer 210 through the turned-on NMOS transistor Q1. The controlled terminal CP of the PWM control chip 210 controls the duty cycle of the output PWM voltage signal after receiving the trigger voltage, thereby avoiding damage to the transformers VF1, VF2 or the light-emitting element L. Obviously, in other embodiments, the NMOS transistor Q1 can be replaced by a high-level conduction switch such as an NPN transistor. The voltage terminal Vad and the reference voltage point can be connected to a power source to obtain a corresponding voltage value.

Please refer to FIG. 5 , which is a specific circuit diagram of the electronic device 1 according to the second embodiment of the present invention. In the present embodiment, the comparison circuit 10 includes a Zener diode ZD, a resistor R2, and an NMOS transistor Q2. The Zener diode ZD and the resistor R2 are connected in series between the primary coil connection node N of the at least two transformers VF1, VF2 and the ground. The gate of the NMOS transistor Q2 is connected to a connection point (not shown) of the Zener diode ZD and the resistor R2, and the source of the NMOS transistor Q2 is grounded. The magnitude of the breakdown voltage of the Zener diode ZD is equal to the reference voltage value.

The adjustment trigger circuit 20 includes a PMOS transistor Q3 and a resistor R3. The PMOS transistor Q3 and the resistor R3 are connected in series between the voltage terminal Vad and the ground. The gate of the PMOS transistor Q3 is connected to the drain of the NMOS transistor Q2 of the comparison circuit 10. The source of the PMOS transistor Q3 is connected to the voltage terminal Vad, and the drain of the PMOS transistor Q3 is connected to the resistor R3. A connection point of the PMOS transistor Q3 and the resistor R3 is connected to the controlled terminal CP of the PWM control wafer 210. Wherein, as described above, the voltage terminal Vad is used to provide the trigger voltage, and the trigger voltage is greater than or equal to a pre-stored safe voltage value in the PWM control chip 210.

Wherein, when the detection voltage, that is, the voltage at the connection point of the at least two transformers VF1, VF2 is greater than the breakdown voltage of the Zener diode ZD, that is, the reference voltage value, the Zener diode ZD is turned on, thereby A current flows through the resistor R2 such that the junction of the Zener diode ZD and the resistor R2 is at a high level. Therefore, the NMOS transistor Q2 is turned on, and the gate of the PMOS transistor Q3 is connected to the ground through the turned-on NMOS transistor Q2 to be at a low level, so that the PMOS transistor is turned on correspondingly. The voltage terminal Vad provides the trigger voltage to the controlled terminal CP of the PWM control wafer 210 through the turned-on PMOS transistor Q3. The controlled terminal CP of the PWM control chip 210 controls the duty cycle of the output PWM voltage signal after receiving the trigger voltage. Obviously, in other embodiments, the NMOS transistor Q2 can be replaced by a high-level conduction switch such as an NPN transistor, and the PMOS transistor Q3 can be replaced by a low-level conduction switch such as a PNP transistor.

Please refer to FIG. 6 , which is a circuit block diagram of an electronic device 1 including a plurality of pairs of transformers according to an embodiment of the present invention. As shown in FIG. 6, when the electronic device 1 includes a plurality of pairs of transformers VF, the primary coils of each pair of transformers VF are connected in series between the output terminals OT1, OT2 of the bridge switching circuit 220. In this embodiment, the protection circuit further includes at least one diode D, and the connection node N of the primary coil of each pair of transformers VF is forwardly connected to the comparison circuit 10 through a diode D, that is, the diode D The connection is positively connected between the connection node N of the primary coil of each pair of transformers VF and the comparison circuit 10. These diodes D are used to avoid voltage interference between each pair of transformers VF. Obviously, when the electronic device 1 includes only a pair of transformers VF, the protection circuit 100 can also include the diode D.

The electronic device 1 can be an illumination device such as a street lamp or an indoor lamp, or can be an electronic device that requires a light-emitting module as a backlight, such as a mobile phone, an e-book, a digital camera, or a tablet computer. The light-emitting element L may be an LED (Light Emitting Diode), a cold cathode fluorescent tube, or the like.

The light-emitting module protection circuit 100 of the present invention and the electronic device 1 having the protection circuit 100 are simple in structure and low in cost. By detecting the voltage of the connection node N of each pair of transformer VF primary coils, it can be determined whether or not the light-emitting element L is abnormal, and correspondingly reducing the duty ratio of the PWM voltage signal outputted by the PWM control chip 210, to the transformer VF or the light-emitting Element L is protected.

1. . . Electronic device

100. . . protect the circuit

300. . . Power interface

210. . . PWM control chip

220. . . Bridge switching circuit

VF1, VF2, VF. . . transformer

L. . . Light-emitting element

IN, IN1. . . Input

CP. . . Controlled end

OT1, OT2, OT. . . Output

FC1, FC2, FC. . . Primary coil

SC1, SC2, SC. . . Secondary coil

10. . . Comparison circuit

20. . . Adjustment trigger circuit

N. . . Connection node

101. . . Comparators

Vref. . . Reference voltage point

Q1, Q2. . . NMOS tube

R1~R3. . . resistance

Vad. . . Voltage terminal

Q3. . . PMOS tube

ZD. . . Zener diode

D. . . Dipole

C. . . High voltage capacitor

FIG. 1 is a circuit diagram of a prior art light emitting module.

2 is a circuit block diagram of an electronic device having a light-emitting module protection circuit according to an embodiment of the present invention.

FIG. 3 is a schematic diagram showing the magnitude of the detected voltage detected by the protection circuit when the light-emitting element operates normally and abnormally in the light-emitting module according to an embodiment of the present invention.

4 is a circuit diagram of an electronic device having a light-emitting module protection circuit according to a first embodiment of the present invention.

FIG. 5 is a circuit diagram of an electronic device having a light-emitting module protection circuit according to a second embodiment of the present invention.

6 is a circuit block diagram of an electronic device having a light-emitting module protection circuit according to another embodiment of the present invention.

1. . . Electronic device

100. . . protect the circuit

300. . . Power interface

210. . . PWM control chip

220. . . Bridge switching circuit

VF1, VF2. . . transformer

L. . . Light-emitting element

IN, IN1. . . Input

CP. . . Controlled end

OT1, OT2, OT. . . Output

FC1, FC2. . . Primary coil

SC1, SC2. . . Secondary coil

10. . . Comparison circuit

20. . . Adjustment trigger circuit

N. . . Connection node

Claims (10)

A light-emitting module protection circuit for protecting a light-emitting module, comprising: a PWM control chip, a bridge switching circuit, at least one pair of transformers, and driving through the PWM control chip, the bridge switching circuit and at least one pair of transformers The improvement of at least two light-emitting elements is that the protection circuit comprises:
a comparison circuit is connected to the primary coil connection node of the at least one pair of transformers for detecting a voltage of the primary coil connection node of the at least one pair of transformers to obtain a detection voltage, and the detection voltage and a reference voltage Comparing values, outputting a detection signal when the detection voltage is greater than the reference voltage value, and an adjustment trigger circuit connected to the comparison circuit and the PWM control chip for outputting when the detection signal is received A trigger voltage is applied to the PWM control chip, and the PWM control chip is triggered to lower the duty ratio of the output PWM voltage signal. The illuminating module protection circuit of claim 1, wherein the comparison circuit comprises a comparator, the inverting input end of the comparator is connected to a reference voltage point for providing the reference voltage value, a non-inverting input of the comparator is coupled to the primary coil connection node of the at least one pair of transformers; the adjustment trigger circuit includes an NMOS transistor and a resistor connected in series with a voltage terminal for providing the trigger voltage and Between the ground, the gate of the NMOS transistor is connected to the output end of the comparator, the source of the NMOS transistor is connected to the voltage terminal, the drain of the NMOS transistor is connected to the resistor, the NMOS transistor and the resistor A connection node is coupled to the PWM control chip. The illuminating module protection circuit of claim 1, wherein the comparison circuit comprises a Zener diode, a first resistor and an NMOS transistor, wherein the Zener diode and the first resistor are connected in series a primary coil of at least two transformers is connected between the node and the ground, a gate of the NMOS transistor is connected to a connection point of the Zener diode and the first resistor, and a source of the NMOS transistor is grounded, and the Zener diode is The magnitude of the breakdown voltage is equal to the reference voltage value; the adjustment trigger circuit includes a PMOS transistor and a second resistor connected in series between a voltage terminal for providing the trigger voltage and ground; the PMOS a gate of the transistor is connected to a drain of the NMOS transistor of the comparison circuit, a source of the PMOS transistor is connected to the voltage terminal, a drain of the PMOS transistor is connected to the second resistor, and a connection between the PMOS transistor and the second resistor is The point is connected to the PWM control chip. The illuminating module protection circuit of claim 1, wherein the protection circuit further comprises at least one diode, the at least one diode is forwardly connected to the primary coil connection node of each pair of transformers and the comparison circuit between. An electronic device includes a power interface, a light emitting module, and a light emitting module protection circuit, wherein the power interface is configured to provide a DC voltage, and the light emitting module includes a PWM control chip, a bridge switching circuit, at least one pair of transformers, and at least two a light-emitting element, the PWM control chip includes an input end, a controlled end, and an output end, the PWM control chip is connected to the power supply interface through an input end, and receives a power supply voltage of the power supply interface to generate a PWM voltage signal through the output end Output, the bridge switching circuit includes an input end and two output ends, the input end of the bridge switching circuit is connected to an output end of the PWM control chip, and the bridge switching circuit is used to output PWM voltage of the PWM control chip Converting the signal into an AC PWM voltage signal and outputting through the two output terminals; at least one pair of transformers are respectively connected between the two output ends of the bridge switching circuit and the at least two light emitting elements for outputting the bridge switching circuit The AC PWM voltage signal is converted into a voltage signal of a suitable size to drive the light emitting element to emit light, and the improvement thereof is The light-emitting module protection circuit comprising:
a comparison circuit is connected to the primary coil connection node of the at least one pair of transformers for detecting a voltage of the primary coil connection node of the at least one pair of transformers to obtain a detection voltage, and the detection voltage and a reference voltage Comparing values, outputting a detection signal when the detection voltage is greater than the reference voltage value; and adjusting the trigger circuit to be connected to the comparison circuit and the controlled end of the PWM control chip for receiving the detection When the signal is output, a trigger voltage is outputted to the controlled end of the PWM control chip, and the PWM control chip is triggered to lower the duty ratio of the output PWM voltage signal. The electronic device of claim 5, wherein the comparison circuit comprises a comparator, the inverting input of the comparator is connected to a reference voltage point for providing the reference voltage value, and the comparator is positive The phase input terminal is connected to the primary coil connection node of the at least one pair of transformers; the adjustment trigger circuit includes an NMOS transistor and a resistor connected in series between a voltage terminal for providing the trigger voltage and the ground, The gate of the NMOS transistor is connected to the output end of the comparator, the source of the NMOS transistor is connected to the voltage terminal, the drain of the NMOS transistor is connected to the resistor, and the connection node of the NMOS transistor and the resistor is The PWM controls the controlled end connection of the wafer. The electronic device of claim 5, wherein the comparison circuit comprises a Zener diode, a first resistor, and an NMOS transistor, the Zener diode and the first resistor being connected in series to the at least two transformers The primary coil is connected between the node and the ground, the gate of the NMOS transistor is connected to the junction of the Zener diode and the first resistor, the source of the NMOS transistor is grounded, and the breakdown voltage of the Zener diode The adjustment trigger circuit includes a PMOS transistor and a second resistor connected in series between a voltage terminal for providing the trigger voltage and ground; a gate of the PMOS transistor Connected to the drain of the NMOS transistor of the comparison circuit, the source of the PMOS transistor is connected to the voltage terminal, the drain of the PMOS transistor is connected to the second resistor, the connection point of the PMOS transistor and the second resistor is connected to the PWM Control the controlled end connection of the wafer. The electronic device of claim 5, wherein the protection circuit further comprises at least one diode, the at least one diode being positively connected between the primary coil connection node of each pair of transformers and the comparison circuit. The electronic device of claim 5, wherein the electronic device is a lighting device including a street lamp and an indoor lamp. The electronic device of claim 5, wherein the electronic device is an electronic device including a mobile phone, an electronic book, a digital camera, and a tablet computer.