LED emergency lighting controller IC with selectable brightness

Abstract

The present invention discloses an LED emergency lighting controller integrated circuit with selectable brightness, which is internally provided with a charge and discharge management circuit, a power grid and switch monitoring circuit, and a brightness selection circuit. The present invention uses analog-digital hybrid technology to realize segmented emergency lighting dimming, which not only reduces the system application cost, but also can select emergency lighting brightness of different segments, thereby realizing the extension of emergency lighting duration.

Description

Technical Field

[0001] The present invention relates to an emergency lighting controller, in particular to an LED emergency lighting controller integrated circuit with selectable brightness, and an emergency lighting fixture comprising the integrated circuit. Background Art

[0002] There is a kind of emergency lighting fixture on the market. After the mains power grid stops supplying electricity, this kind of lamp can still provide emergency lighting for a period of time. This is of practical value to the vast underdeveloped areas of the world. This kind of emergency lighting fixture has been available since the era of energy-saving fluorescent lamps more than ten years ago. When the mains power grid is supplying electricity normally, they provide normal lighting and charge the lithium battery in the lamp to store energy. After the power grid stops supplying electricity, the lithium battery is discharged to provide emergency lighting for a limited time.

[0003] After entering the LED lighting era, LED emergency lighting fixtures also appeared. Figure 1 The circuit structure of the first generation of LED emergency lighting fixtures in the prior art is shown. Among them, the lithium battery 130 is an energy storage element, the load 170 is the main light source when the power grid is normally powered, and the load 190 is the emergency light source after the power grid stops supplying power. When the main power grid is normally powered, the lamp switch 110 controls the on and off of the main light source 170. After the switch 110 is closed, the main light source 170 outputs light and charges the lithium battery through the linear charging control circuit 300; at the same time, the power grid state monitoring circuit 100 recognizes that the power grid state is normally powered, turns off the discharge PNP transistor 014, and the emergency light source 190 has no light output. After the power grid stops supplying power, the main light source 170 has no light output, and the switch 110 controls the on and off of the emergency light source 190; at the same time, the power grid state monitoring circuit 100 recognizes that the power grid state is a power outage (at this time, the switch 110 is in a closed state), turns on the discharge PNP transistor 014, and the lithium battery 130 discharges the emergency light source 190 through the PNP tube 014 and the resistor 015 to provide emergency lighting.

[0004] When the lamp switch 110 is disconnected, no matter the main power grid is powered normally or out of power, the main light source 170 and the emergency light source 190 have no light output. In this case, it is obvious that the main light source 170 has no light output. When the switch 110 is in the disconnected state, the positive electrode voltage BAT of the lithium battery 130 reaches the switch constant current control circuit 200 through the resistors 007, 005, 004 and the rectifier bridge 120. The maximum voltage of BAT is 4.2V. At this voltage, the operating current of the switch constant current control circuit 200 is very small, generally below 1uA. In this way, the terminal voltage of the resistor 007 is below 0.1V, the PNP transistor 008 is in the off state, the NPN transistor 013 and the PNP transistor 014 are also turned off, and the emergency light source 190 has no light output.

[0005] When the switch 110 is in a short-circuited state, the state of the main power grid determines whether the main light source 180 has light output or the emergency light source 190 has light output. When the grid is powered normally, it is easy to understand that the main light source 170 is bright. When the switch 110 is in a closed state and the grid is powered normally, the grid charges and discharges the capacitor 002 through resistors 004, 005, 001 and diode 003. Since the unidirectional conduction impedance of the diode 003 is much smaller than the resistance of the resistor 005, the charging speed of the capacitor 002 is much greater than the discharging speed, so that the voltage at the end of the capacitor 002 will increase rapidly. When the voltage at the end of the capacitor 002 is greater than the voltage of the lithium battery 130, the transistor 008 is turned off, the NPN transistor 013 and the PNP transistor 014 are also turned off, and the emergency light source 190 has no light output.

[0006] When the switch 110 is in the closed state, but the power grid is in a power outage state, the power grid state monitoring circuit 100 detects the DC impedance between the live wire and the neutral wire through resistors 004, 005, 007, and 001. If the impedance between the live wire and the neutral wire is less than 500K, the voltage at the end of resistor 007 will be greater than 0.3V, the PNP transistor 008 will enter a slightly open state, and the emergency light source 190 will have light output. If the impedance between the live wire and the neutral wire is greater than 500K, the emergency light source 190 will have no light output. In the power grid power outage state, the resistance between the live wire and the neutral wire is generally much lower than 500K, which is because a large number of electrical equipment are connected in parallel to the power grid; this is also the basis for the emergency lighting fixture to control the emergency light source 190 to turn on and off through the switch 110 in the power outage state.

[0007] The charging of the lithium battery 130 is realized by the linear charging control circuit 300. The load voltage of the main light source 170 is first reduced by the transformer 161, and then rectified by the diode 150 and filtered by the capacitor 140 to obtain a charging voltage close to the voltage of the lithium battery 130.

[0008] The above-mentioned emergency lighting fixtures have the following defects: first, the duration of emergency lighting is short, only two to three hours, while in some underdeveloped countries and regions, power outages of more than one day often occur; second, there are too many components in the lamps, resulting in low production efficiency. Summary of the invention

[0009] The purpose of the present invention is to address the above defects of LED emergency lighting fixtures in the prior art and to significantly extend the duration of emergency lighting without increasing the cost of the fixtures.

[0010] According to a first aspect of the present invention, there is provided an LED emergency lighting controller integrated circuit with selectable brightness, which is internally provided with a charge and discharge management circuit, a power grid and switch monitoring circuit and a brightness selection circuit, wherein the charge and discharge management circuit is connected between a BAT node between an LED main light source and an energy storage battery located outside the integrated circuit and the LED emergency light source, and when the voltage of the BAT node reaches a first reference voltage, the charging current of the energy storage battery is bypassed and discharged to the LED emergency light source; the power grid and switch monitoring circuit is connected to the AC power grid via an external control switch, detects power supply, power outage and closing and disconnection of the control switch, and generates an emergency light source on / off signal; the brightness selection circuit receives the emergency light source on / off signal and generates an emergency light source dimming signal to the charge and discharge management circuit.

[0011] According to a second aspect, an emergency lighting fixture is provided, comprising an integrated circuit, a constant current control circuit, an LED main light source, a storage battery and an LED emergency light source as described in the first aspect above, wherein the constant current control circuit provides a constant operating current for the LED main light source.

[0012] According to the present invention, the LED emergency lighting controller integrated circuit uses analog-digital hybrid technology to achieve segmented emergency lighting dimming, which not only reduces the system application cost, but also allows the selection of emergency lighting brightness at different levels, thereby extending the duration of emergency lighting. The lower the selected emergency lighting brightness, the longer the corresponding lighting duration. The present invention has practical value for the vast majority of underdeveloped countries and regions. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to better understand the present invention, the present invention is further described below with reference to embodiments in conjunction with the accompanying drawings. In the accompanying drawings:

[0014] Figure 1 The circuit structure of the first generation LED emergency lighting fixture in the prior art is shown;

[0015] Figure 2 This is a circuit diagram of an LED emergency lighting fixture according to an embodiment of the present invention;

[0016] Figure 3 for Figure 2 An example of a circuit for monitoring the power grid and switches, and a circuit for selecting brightness;

[0017] Figure 4 for Figure 2 Another example of a medium power grid and switch monitoring circuit and brightness selection circuit;

[0018] Figure 5 This is a circuit diagram of an LED emergency lighting fixture according to another embodiment of the present invention;

[0019] Figure 6 This is a circuit structure diagram of an LED emergency lighting fixture according to another embodiment of the present invention;

[0020] Figure 7 for Figure 6 An example of a medium brightness selection circuit. DETAILED DESCRIPTION

[0021] The inventors considered that, without increasing the cost of the lamp (for example, the capacity of the lithium battery does not increase), the duration of emergency lighting can be extended to a certain extent by selecting different emergency lighting brightness. For example, if the duration of emergency lighting is to be increased three times, the emergency lighting brightness should be reduced three times; if the duration of lighting is to be increased ten times, the lighting brightness should be reduced ten times. In other words, the inventors need to consider how to select different emergency lighting brightnesses through lamp switches. Obviously, Figure 1 The solution uses pure analog technology. However, the present invention must use a hybrid technology of analog and digital to achieve the selection of emergency lighting brightness.

[0022] Figure 2 FIG. 1 is a circuit diagram of an LED emergency lighting fixture according to an embodiment of the present invention. Figure 2 As shown, the lamp includes an LED emergency lighting controller integrated circuit 400, a constant current control circuit 200, an LED main light source 170, an energy storage battery (such as a lithium battery) 130, and an LED emergency light source 190. When the AC power supply is normal and the external control switch 110 is closed, the constant current control circuit 200 provides a constant working current for the main light source 170, and this current is also the charging current of the lithium battery 130.

[0023] Inside the emergency lighting controller integrated circuit 400, there are provided a charge and discharge management circuit 450, a power grid and switch monitoring circuit 410 and a brightness selection circuit 430. Among them, the charge and discharge management circuit 450 is connected between the external BAT node and the emergency light source 190, and the BAT node is the node between the main light source 170 and the lithium battery 130; when the battery voltage BAT reaches a reference voltage (such as 4.2V), the charge and discharge management circuit 450 bypasses the charging current of the lithium battery 130 and discharges it to the emergency light source 190. The power grid and switch monitoring circuit 410 is connected to the AC power grid through the external control switch 110, detects the power supply, power failure of the power grid and the closing and disconnection status of the control switch 110, and generates an emergency light source on / off signal EON. The brightness selection circuit 430 receives the emergency light source on / off signal EON and generates an emergency light source dimming signal to the charge and discharge management circuit 450.

[0024] The charge and discharge management circuit 450 is composed of a discharge PMOS tube 461 and an error amplifier 451. Figure 2As shown, the source of the discharge PMOS tube 461 is connected to the BAT node, and the drain is connected to the emergency light source 190; the positive input terminal of the error amplifier 451 is connected to the reference voltage 4.2V, the negative input terminal is connected to the BAT node, and the output terminal is connected to the gate of the discharge PMOS tube 461; when the battery voltage BAT reaches 4.2V, the error amplifier 451 linearly turns on the discharge PMOS tube 461 to bypass the excessive charging current to the emergency light source 190. When the lithium battery 130 is fully charged, the working current of the main light source 170 will be completely bypassed to the emergency light source 190 through the PMOS tube 461. At this time, the light output by the emergency light source 190 is much smaller than that of the main light source 170. At this stage, the emergency light source dimming signal output by the brightness selection circuit 430 to the gate of the PMOS tube 461 is in a high impedance state, with neither current output nor voltage output, and thus will not have any effect on the operation of the error amplifier 451. The error amplifier 451 outputs a high impedance, small current control signal.

[0025] When the switch 110 is disconnected (regardless of whether the power grid is powered), the constant current control circuit 200 stops working, and the main light source 170 has no light output. The power grid and switch monitoring circuit 410 will recognize that the switch 110 is in the disconnected state, and output the emergency light source off signal EON, so that the emergency light source dimming signal output by the brightness selection circuit 430 is always in a high impedance state, so that the PMOS tube 461 is in a closed state under the control of the error amplifier 451, and the emergency light source 190 has no light output.

[0026] When the switch 110 is closed in the power grid, the power grid and switch monitoring circuit 410 will recognize that the switch 110 is in the closed state, and output the emergency light source on signal EON, so that the brightness selection circuit 430 generates a PWM emergency light source dimming signal with a predetermined duty cycle, and this PWM signal determines the on duty cycle of the PMOS tube 461. Assuming that the PWM signal duty cycle is D, the on duty cycle of the PMOS tube 461 is 1-D. The on duty cycle of the PMOS tube 461 is the duty cycle of the light output of the emergency light source 190. The larger the on duty cycle of the PMOS tube 461, the brighter the emergency light source 190. Therefore, by selecting different PWM duty cycles, different emergency lighting brightness can be selected, thereby achieving different maximum emergency lighting times. That is, the higher the emergency lighting brightness, the shorter the lighting duration; conversely, the lower the emergency lighting brightness, the longer the corresponding lighting duration.

[0027] Reference Figure 3 , Figure 3 for Figure 2The power grid and switch monitoring circuit 410 is an example of a brightness selection circuit. The power grid and switch monitoring circuit 410 includes a first and a second comparison circuit, an OR gate 420, a timer 422, an inverter 424, and an emergency status register 425. The first comparison circuit is used to detect the power supply and power failure status of the power grid, and its output end is connected to an input end of the OR gate 420; the second comparison circuit is used to detect the closing and opening status of the control switch 110, and its output end is connected to the other input end of the OR gate 420; the output end of the OR gate 420 is connected to the reset end RST1 of the timer 422; the output end of the timer 422 is connected to the clock end CK of the emergency status register 425 through the inverter 424; the reset end R of the emergency status register 425 is connected to the output end of the OR gate 420, and its output end generates the emergency light source on / off signal EON.

[0028] The grid and switch monitoring circuit 410 may further include an inverter 419 and a timer 421. The output terminal of the second comparison circuit is connected to a reset terminal RST0 of the timer 421 via the inverter 419, and the timer 421 outputs a timing signal S10.

[0029] The first comparison circuit can be composed of a comparator 418 and resistors 412 and 413. The resistors 412 and 413 are connected in series between one of the live wire and the neutral wire and the reference ground GND; one input terminal of the comparator 418 is connected to the node between the resistors 412 and 413, the other input terminal is connected to a reference voltage (such as 1V), and the output terminal is connected to an input terminal of the OR gate 420.

[0030] The second comparison circuit can be composed of a comparator 417, a current mirror, and resistors 416 and 411. The sources of the current mirror input and output PMOS tubes 415 and 414 are connected to the BAT node, and the gate and drain of the input PMOS tube 415 are connected to the reference ground GND via the resistor 416; one input end of the comparator 417 is connected to the other of the live wire and the neutral wire via the resistor 411, and the drain of the current mirror output PMOS tube 414 is connected to the node between the resistor 411 and the input end, and the other input end of the comparator 417 is connected to a reference voltage (such as BAT-1V), and its output end is connected to the other input end of the OR gate 420 and the input end of the inverter 419.

[0031] In this example, the resistance of resistors 411 and 412 can be selected between 200K and 300K. If the resistance is too small, too much power loss will be generated, especially after integration into the chip, the power consumption will affect the chip safety; if the resistance is too large, the monitoring sensitivity will be insufficient. Relative to the ground GND of the rectifier bridge, AC1 / AC2 are both half-wave sine waves with a frequency of 50HZ and a phase difference of 180 degrees.

[0032] Comparator 418 is responsible for detecting whether the AC power supply is normal or not. The AC2 voltage is divided by resistors 412 and 413 to obtain AC2IN, which is sent to one input terminal of comparator 418, and the other input terminal thereof is connected to a reference voltage 1V, for example. When the AC power supply is normal and the control switch 110 is closed, AC2IN is a positive half-wave sine wave, which is greater than 1V for nearly half of the time, so the output ACON of comparator 418 is a high level "1" for half of the time. The signal ACON is 1, indicating that the AC power supply is normal, which means that the emergency light source 190 cannot be turned on, that is, the signal EON is 0.

[0033] Comparator 417 is responsible for detecting whether the control switch 110 is closed or open. When the switch 110 is open, the output signal SOFF of comparator 417 is always 1. The input PMOS tube 415 and the output PMOS tube 414 form a 1:1 current mirror, and the resistance value of resistor 416 can be selected as 1 megohm, for example. The current flowing through resistor 416 is approximately equal to (BAT-1V) / R416. For example, when BAT is equal to 4V, the current mirror input current is approximately 3uA. Therefore, the maximum output current of the current mirror is also 3uA (when AC1IN<BAT-1V), and the minimum output current is zero (when AC1IN=BAT). When the switch 110 is open, no current flows out of the PMOS tube 414, so AC1IN=BAT, and the output SOFF of comparator 417 is high.

[0034] The emergency state register 425 is, for example, a falling edge triggered D flip-flop, the level of its Q output terminal EON determines whether the emergency light source is turned on, EON is 0, indicating that the emergency light source 190 is turned off, and EON is 1, indicating that the emergency light source 190 is turned on; its reset terminal R signal comes from the logical OR result of the comparator 417 output SOFF and the comparator 418 output ACON. This means that when the switch 110 is disconnected (regardless of whether the AC power grid is out of power), or when the AC power is detected to be normally supplied, the emergency state register 425 will be cleared, that is, EON is 0, and the emergency light source 190 is turned off.

[0035] There is another situation, that is, the AC power grid is out of power and the switch 110 is closed. Assuming that AC1 and AC2 are in a short-circuit state, the current output by the current mirror of the PMOS tube 414, for example, 3uA (corresponding to BAT is 4V) flows through the resistor 411, then to the resistor 412, and finally to the reference ground GND through the resistor 413. The voltage generated on the resistor 413 is 60mV, that is, AC2IN is 60mV, and the comparator 418 outputs the signal ACON as 0. The sum of the voltages on the resistors 411, 412, and 413 is 1260mV, that is, AC1IN is 1260mV, and the comparator 417 outputs the signal SOFF as 0. When the signals ACON and SOFF are both zero, the timer 422 (for example, a 100 millisecond timer) starts timing. After 100 milliseconds have elapsed, the output signal generates a falling edge through the inverter 424 to trigger the emergency status register 425. After the triggering, the output Q end of the register 425 is equal to its D input end (i.e., BAT), that is, EON is 1, and the emergency light source 190 is turned on. Thereafter, once the switch 110 is disconnected, the signal SOFF becomes high, and the timer 422 and the emergency status register 425 are both cleared, that is, EON is 0, and the emergency light source 190 is turned off. In this way, the on and off of the emergency light source 190 is controlled by the switch 110 during a power outage.

[0036] Figure 3 In the example, the brightness selection circuit 430 includes an inverter 438, an OR gate 439, a brightness state register 431, and a brightness decoding circuit. Among them, one input end of the OR gate 439 is connected to the output end of the timer 421, the other input end is connected to the output end of the comparator 418, and its output end is connected to the reset end R of the brightness state register 431; the clock end CK of the brightness state register 431 is connected to the output end of the emergency state register 425 via the inverter 438; the brightness decoding circuit can be composed of an AND gate 432, an OR gate 433, PMOS tubes 434, 435 and NMOS tubes 436, 437. The circuit generates an emergency light source dimming signal based on the emergency light source on / off signal EON, the state information output by the brightness state register 431, and a continuous pulse signal with a predetermined duty cycle (for example, 30%).

[0037] For example, the brightness state register 431 may use a binary asynchronous counter to store brightness information, and the reset state corresponds to the default brightness. The register 431 is triggered to flip at the falling edge of EONB, that is, it is triggered to flip at the rising edge of each EON. Its reset signal has two sources: one is ACON, which means that the register will be reset when the AC power supply is normal; the other is that after the switch 110 is disconnected, that is, SOFF is 1, the timer 421 will also reset the register after counting for 10 seconds, for example.

[0038] When the emergency light source 190 is turned off, the signal EON is 0, and the signal EONB is 1, and the PMOS tube 434 and the NMOS tube 437 of the brightness decoding circuit are both turned off, so the output emergency light source dimming signal is in a high impedance state. When the signal EON is 1 and EONB is 0, the emergency light source 190 is turned on. The first rising edge of EON triggers the register 431 to flip, and its Q terminal is high level. After passing through the OR gate 433, the output emergency light source dimming signal is always low level, so that the discharge PMOS tube 461 in the charge and discharge management circuit 450 is fully turned on to provide the maximum current for the emergency light source 190. After the switch 110 is disconnected, for example, the switch 110 is closed again within 10 seconds, and a second EON rising edge is generated. The register 431 will flip again, and its QB terminal is high level, so that the continuous pulse signal with a duty cycle of, for example, 30% connected to the AND gate 432 is output to the PWM node, D (PWM) = 1-30% = 70%, and the opening time of the discharge PMOS tube 461 is 30%, and the corresponding brightness is 30% of the maximum brightness. In this way, through the closing and opening operations of the switch 110, the selection of the output luminous flux (brightness) of the emergency light source 190 is realized.

[0039] In this example, the brightness state register 431 uses a binary asynchronous counter, corresponding to two sections of brightness selection, the first section is the maximum brightness of 100%, the second section is the energy-saving gear, such as 30% brightness, and then the maximum brightness again, in turn. Here, the brightness state register 431 can also use a ternary or quaternary asynchronous counter, corresponding to three or four sections of brightness selection, respectively, and the working principle of the corresponding brightness decoding circuit is the same. In real applications, the three-section brightness selection can be, the first section is the maximum brightness of 100%, the second section is the energy-saving gear (such as 30%), and the third section is the super energy-saving gear (such as 10%). The four-section brightness selection can be, the first section is the maximum brightness of 100%, the second section is the energy-saving gear (such as 30%), the third section is the super energy-saving gear (such as 10%), and the fourth section is the extreme energy-saving gear (such as 3%, equivalent to the light emitted by a candle).

[0040] according to Figure 3 For example, in the use of power outage emergency lighting, if the switch 110 is disconnected for more than a certain time (e.g., 10 seconds), the emergency lighting brightness state will be reset. In real application scenarios, it will be of practical significance if the emergency lighting status information can be stored for a long time. In particular, the standby time of lithium batteries is very long, and it is possible to realize the emergency lighting brightness memory function. For example, if you know that the power outage will last for a long time, you hope that the brightness will be 30% every time you turn on the light.

[0041] Figure 4 for Figure 2 Another example of a power grid and switch monitoring circuit and a brightness selection circuit in FIG. In this example, the power grid and switch monitoring circuit 410 and Figure 3 The same example, the brightness selection circuit 530 has a memory function. Figure 4 As shown, the brightness selection circuit 530 includes an inverter 438, OR gates 542 and 543, a mask register 541, a brightness state register 531, and a brightness decoding circuit. Among them, one input end of the OR gate 542 is connected to the output end of the timer 421, the other input end is connected to the output end of the comparator 418, and its output end is connected to the reset end R of the mask register 541; the clock end CK of the mask register 541 is connected to the output end of the emergency state register 425; one input end of the OR gate 543 is connected to the inverting output end of the mask register 541, and the other input end is connected to the output end of the emergency state register 425 through the inverter 438, and its output end is connected to the clock end CK of the brightness state register 531; the reset end R of the brightness state register 531 is connected to the output end of the comparator 418; the composition of the brightness decoding circuit is similar to Figure 3 Same examples.

[0042] The working principle of the brightness selection circuit 530 is described as follows. During emergency lighting, if the switch 110 is disconnected for more than, for example, 10 seconds before turning on the light, the first EON rising edge generated will be shielded and will not be transmitted to the brightness status register 531, so that the last emergency brightness information will not change, thereby realizing the memory function. The key to shielding the first EON rising edge is the falling edge shielding register 541. During emergency lighting, whenever the light is turned off for more than, for example, 10 seconds, the shielding register 541 will be reset, and its QB terminal will be high. After the first subsequent EON rising edge arrives, since the shielding register 541 is triggered by the falling edge, it will not be flipped by the EON rising edge trigger, and its QB terminal will always be high. This level shields the first EON falling edge through the OR gate 543, and the brightness status register 531 will not flip, thereby realizing the memory of the emergency brightness information. After the emergency light is turned off, an EON falling edge will be generated, causing the shielding register 541 to trigger the flip, and the shielding function is released. As long as the light is turned on again within 10 seconds after being turned off, the new EON rising edge will trigger the brightness status register 531 to flip, and the new emergency lighting brightness will be obtained after decoding. In order to ensure the brightness synchronization consistency when multiple emergency lighting fixtures are used in parallel (which may accidentally cause the brightness status of each lamp to be inconsistent), each time the AC power supply is normal (ACON=1), the brightness status register 531 and the mask register 541 will be reset.

[0043] Reference Figure 5 , Figure 5 FIG. 1 is a circuit diagram of an LED emergency lighting fixture according to another embodiment of the present invention. Figure 2The difference between the two schemes is that the charge and discharge management circuit 650 is composed of a discharge NMOS tube 661 and an error amplifier 451. Among them, the source of the discharge NMOS tube 661 is connected to the reference ground GND, and the drain is connected to the emergency light source 190; the positive input terminal of the error amplifier 451 is connected to the positive electrode BAT node of the lithium battery 130, the negative input terminal is connected to a reference voltage (for example, 4.2V), and the output terminal is connected to the gate of the discharge NMOS tube 661; when the BAT node voltage reaches the above reference voltage, the error amplifier 451 linearly turns on the discharge NMOS tube 661. In addition, the brightness selection circuit 630 generates an emergency light source dimming signal to the gate of the discharge NMOS tube 661. Here, only the polarity of the signal output by the brightness selection circuit 630 is different from Figure 2 The signals are opposite, and the other circuit logics are the same, so I will not go into details.

[0044] Compared with PMOS tubes, the benefits of using NMOS tubes as emergency discharge tubes are more obvious. Since the carriers of NMOS tubes are electrons, their mobility is two to three times faster than that of PMOS hole carriers, so the on-resistance Rdson of NMOS tubes is two to three times smaller than that of PMOS tubes of the same area. In other words, to achieve the same Rdson (generally less than 0.3 ohms), the area of ​​NMOS tubes can be two to three times smaller than that of PMOS tubes, which is very valuable for reducing costs, especially when Rdson is small.

[0045] In the above example of the present invention, digital dimming PWM technology is used to change the emergency lighting brightness of the lamp. The digital dimming method has the advantages of high efficiency and stable multi-stage brightness ratio, but it also has the disadvantage of flickering of the output light. The lower the PWM frequency, the more serious the flicker, which is not good for human eyesight. The advantages and disadvantages of analog dimming technology are exactly the opposite of digital dimming technology. The present invention can also use analog dimming technology to change the emergency lighting brightness of the lamp.

[0046] Figure 6 FIG. 1 is a circuit diagram of an LED emergency lighting fixture according to another embodiment of the present invention. This example uses analog dimming technology and can select two brightness levels. Figure 6As shown, the charge and discharge management circuit 750 includes a main discharge PMOS tube 461, a sub-discharge PMOS tube 761 and an error amplifier 451. Among them, the source of the main and sub-discharge PMOS tubes 461 and 761 are connected to the BAT node, and the drain is connected to the emergency light source 190; the positive input terminal of the error amplifier 451 is connected to a reference voltage (for example, 4.2V), the negative input terminal is connected to the BAT node, and the output terminal is connected to the gate of the main discharge PMOS tube 461; when the BAT node voltage reaches the above reference voltage, the error amplifier 451 linearly turns on the main discharge PMOS tube 461. In addition, the brightness selection circuit 730 generates simulated emergency light source dimming signals MS and SL to the gates of the main and sub-discharge PMOS tubes 461 and 761. It can be seen that the gate of the main discharge PMOS tube 461 is controlled by both the output of the error amplifier 451 and the brightness selection circuit 730; the gate of the sub-discharge PMOS tube 761 is only controlled by the brightness selection circuit 730. The size of the main discharge PMOS tube 461 is several times larger than that of the auxiliary discharge PMOS tube 761, usually 3 to 5 times larger. The larger the multiple, the greater the difference in brightness between the two stages of emergency lighting.

[0047] Figure 7 for Figure 6 An example of a brightness selection circuit in FIG. 730. In this example, the brightness selection circuit 730 has a memory function. In the first stage of emergency lighting, MS is 0 and SL is 1, the main discharge PMOS tube 461 is turned on, the auxiliary discharge PMOS tube 761 is turned off, and the emergency lighting is at the maximum brightness; in the second stage, MS is 1 and SL is 0, the main discharge PMOS tube 461 is turned off, the auxiliary discharge PMOS tube 761 is turned on, and the emergency lighting is at power-saving brightness. During normal AC power supply, the MS node is high impedance, the main discharge PMOS tube 461 is only controlled by the error amplifier 451, and the auxiliary discharge PMOS tube 761 is turned off.

[0048] Figure 6 In the example, the discharge tube can also be an NMOS tube, and the working principle is the same as that of the PMOS discharge tube; and two or three auxiliary discharge tubes can also be used, and their connection in the circuit is the same as Figure 6 The two auxiliary discharge tubes can meet the needs of three-stage brightness selection. The main and auxiliary discharge tubes are all turned on, corresponding to the maximum brightness; the main discharge tube is turned off and the two auxiliary discharge tubes are turned on, corresponding to the second stage of brightness; the main discharge tube and the first auxiliary discharge tube are turned off and the second auxiliary discharge tube is turned on, corresponding to the third stage of brightness. Similarly, three auxiliary discharge tubes are required to achieve four-stage brightness selection. The main and auxiliary discharge tubes are all turned on, corresponding to the maximum brightness; the main discharge tube is turned off and the three auxiliary discharge tubes are turned on, corresponding to the second stage of brightness; the main discharge tube and the first auxiliary discharge tube are turned off and the second and third auxiliary discharge tubes are turned on, corresponding to the third stage of brightness; the main discharge tube and the first and second auxiliary discharge tubes are turned off and the third auxiliary discharge tube is turned on, corresponding to the fourth stage of brightness, which is also the darkest brightness.

[0049] It is obvious that many variations are possible in the invention described herein, which variations cannot be considered as departing from the spirit and scope of the invention. Therefore, all variations obvious to those skilled in the art are included within the scope of the appended claims.

Claims

1. An LED emergency lighting controller integrated circuit with selectable brightness, which has a charge and discharge management circuit, a power grid and switch monitoring circuit and a brightness selection circuit, wherein: A charge and discharge management circuit is connected between a BAT node between the LED main light source and the energy storage battery located outside the integrated circuit and the LED emergency light source, and when the voltage of the BAT node reaches a first reference voltage, the charging current of the energy storage battery is bypassed and discharged to the LED emergency light source; The power grid and switch monitoring circuit is connected to the AC power grid via an external control switch, and generates an emergency light source shutdown signal when the control switch is detected to be disconnected, or when the power grid is detected to be powered and the control switch is closed; generates an emergency light source startup signal when the power grid is detected to be out of power and the control switch is closed; The brightness selection circuit receives the emergency light source on / off signal, generates a high-impedance emergency light source dimming signal to the charge and discharge management circuit based on the emergency light source off signal; and generates a PWM emergency light source dimming signal with a predetermined duty cycle to the charge and discharge management circuit based on the emergency light source on signal.

2. The integrated circuit according to claim 1, wherein: The charge and discharge management circuit includes a discharge PMOS tube and an error amplifier, wherein: A discharge PMOS tube, with a source connected to the BAT node and a drain connected to the LED emergency light source; an error amplifier, wherein the positive input terminal is connected to the first reference voltage, the negative input terminal is connected to the BAT node, and the output terminal is connected to the gate of the discharge PMOS tube; when the BAT node voltage reaches the first reference voltage, the discharge PMOS tube is linearly turned on; Furthermore, the brightness selection circuit generates the emergency light source dimming signal to the gate of the discharge PMOS tube.

3. The integrated circuit according to claim 1, wherein: The charge and discharge management circuit includes a discharge NMOS tube and an error amplifier, wherein: A discharge NMOS tube, with a source connected to the reference ground and a drain connected to the LED emergency light source; an error amplifier, wherein the positive input terminal is connected to the BAT node, the negative input terminal is connected to the first reference voltage, and the output terminal is connected to the gate of the discharge NMOS tube; when the voltage of the BAT node reaches the first reference voltage, the discharge NMOS tube is linearly turned on; Furthermore, the brightness selection circuit generates the emergency light source dimming signal to the gate of the discharge NMOS tube.

4. The integrated circuit according to claim 1, wherein: The power grid and switch monitoring circuit includes a first and a second comparison circuit, a first OR gate, a first timer, a first inverter and an emergency status register, wherein: A first comparison circuit, for detecting the power supply and power outage status of the power grid, wherein an output end of the comparison circuit is connected to an input end of the first OR gate; A second comparison circuit, for detecting the closing and opening status of the control switch, wherein the output end of the comparison circuit is connected to the other input end of the first OR gate; A first OR gate, an output end of which is connected to a reset end of a first timer; A first timer, an output end of which is connected to a clock end of an emergency status register via the first inverter; The emergency status register has a reset terminal connected to the output terminal of the first OR gate, and an output terminal thereof generates the emergency light source on / off signal.

5. The integrated circuit according to claim 4, characterized in that The power grid and switch monitoring circuit also includes a second inverter and a second timer. The output end of the second comparison circuit is connected to the reset end of the second timer via the second inverter. The second timer outputs a timing signal.

6. The integrated circuit according to claim 5, characterized in that The first comparison circuit is composed of a first comparator and first and second resistors, wherein the first and second resistors are connected in series between one of the live wire and the neutral wire and a reference ground; one input end of the first comparator is connected to a node between the first resistor and the second resistor, the other input end is connected to a second reference voltage, and the output end is connected to an input end of the first OR gate; The second comparison circuit is composed of a second comparator, a current mirror and third and fourth resistors; the source of the current mirror input and output PMOS tubes are connected to the BAT node, and the gate and drain of the input PMOS tube are connected to the reference ground via the third resistor; one input end of the second comparator is connected to the other of the live wire and the neutral wire via the fourth resistor, the drain of the current mirror output PMOS tube is connected to the node between the fourth resistor and the input end, the other input end of the second comparator is connected to the third reference voltage, and the output end is connected to the other input end of the first OR gate and the input end of the second inverter.

7. The integrated circuit according to claim 6, characterized in that The brightness selection circuit includes a third inverter, a second OR gate, a brightness state register and a brightness decoding circuit, wherein: A second OR gate, one input end of which is connected to the output end of the second timer, the other input end of which is connected to the output end of the first comparator, and the output end of which is connected to the reset end of the brightness status register; A brightness status register, wherein the clock end is connected to the output end of the emergency status register via a third inverter; The brightness decoding circuit generates the emergency light source dimming signal based on the emergency light source on / off signal, the status information output by the brightness status register and a continuous pulse signal with a predetermined duty cycle.

8. The integrated circuit according to claim 6, wherein: The brightness selection circuit has a memory function.

9. The integrated circuit according to claim 8, characterized in that The brightness selection circuit includes a third inverter, a second and a third OR gate, a mask register, a brightness state register and a brightness decoding circuit, wherein: A second OR gate, one input end of which is connected to the output end of the second timer, the other input end of which is connected to the output end of the first comparator, and the output end of which is connected to the reset end of the mask register; A shielding register, wherein the clock end is connected to the output end of the emergency status register; A third OR gate, one input end of which is connected to the inverting output end of the shielding register, the other input end of which is connected to the output end of the emergency status register via a third inverter, and the output end of which is connected to the clock end of the brightness status register; A brightness status register, a reset terminal of which is connected to the output terminal of the first comparator; The brightness decoding circuit generates the emergency light source dimming signal based on the emergency light source on / off signal, the status information output by the brightness status register and a continuous pulse signal with a predetermined duty cycle.

10. The integrated circuit according to claim 7 or 9, characterized in that The brightness status register adopts a binary, ternary or quaternary asynchronous counter, corresponding to two-stage selectable brightness, three-stage selectable brightness or four-stage selectable brightness respectively.

11. An LED emergency lighting controller integrated circuit with selectable brightness, which has a charge and discharge management circuit, a power grid and switch monitoring circuit and a brightness selection circuit, wherein: A charge and discharge management circuit is connected between a BAT node between the LED main light source and the energy storage battery located outside the integrated circuit and the LED emergency light source, and when the voltage of the BAT node reaches a first reference voltage, the charging current of the energy storage battery is bypassed and discharged to the LED emergency light source; The grid and switch monitoring circuit is connected to the AC grid via an external control switch to detect grid power supply, power failure, and the closing and opening status of the control switch, and generate an emergency light source on / off signal; A brightness selection circuit receives the emergency light source on / off signal and generates an emergency light source dimming signal to the charge and discharge management circuit; The charge and discharge management circuit includes a main discharge PMOS tube, one to three auxiliary discharge PMOS tubes and an error amplifier, wherein: A main discharge PMOS tube and one to three auxiliary discharge PMOS tubes, with sources connected to the BAT node and drains connected to the LED emergency light source; an error amplifier, wherein the positive input terminal is connected to the first reference voltage, the negative input terminal is connected to the BAT node, and the output terminal is connected to the gate of the main discharge PMOS tube; when the BAT node voltage reaches the first reference voltage, the main discharge PMOS tube is linearly turned on; Furthermore, the brightness selection circuit generates a simulated emergency light source dimming signal to the gates of the main discharge PMOS tube and one to three auxiliary discharge PMOS tubes.

12. An LED emergency lighting controller integrated circuit with selectable brightness, which has a charge and discharge management circuit, a power grid and switch monitoring circuit and a brightness selection circuit, wherein: A charge and discharge management circuit is connected between a BAT node between the LED main light source and the energy storage battery located outside the integrated circuit and the LED emergency light source, and when the voltage of the BAT node reaches a first reference voltage, the charging current of the energy storage battery is bypassed and discharged to the LED emergency light source; The grid and switch monitoring circuit is connected to the AC grid via an external control switch to detect grid power supply, power failure, and the closing and opening status of the control switch, and generate an emergency light source on / off signal; A brightness selection circuit receives the emergency light source on / off signal and generates an emergency light source dimming signal to the charge and discharge management circuit; The charge and discharge management circuit includes a main discharge NMOS tube, one to three auxiliary discharge NMOS tubes and an error amplifier, wherein: A main discharge NMOS tube and one to three auxiliary discharge NMOS tubes, the sources of which are all connected to the reference ground, and the drains of which are all connected to the LED emergency light source; an error amplifier, wherein the positive input terminal is connected to the BAT node, the negative input terminal is connected to the first reference voltage, and the output terminal is connected to the gate of the main discharge NMOS tube; when the BAT node voltage reaches the first reference voltage, the main discharge NMOS tube is linearly turned on; Furthermore, the brightness selection circuit generates a simulated emergency light source dimming signal to the gates of the main discharge NMOS tube and one to three auxiliary discharge NMOS tubes.

13. An emergency lighting fixture, characterized in that: It comprises an integrated circuit, a constant current control circuit, an LED main light source, an energy storage battery and an LED emergency light source as described in any one of claims 1 to 12, wherein the constant current control circuit provides a constant operating current for the LED main light source.

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