JP6589581B2 - Emergency lighting system - Google Patents

Description

  The present invention relates to an emergency lighting device used in an emergency such as a power failure.

  The emergency lighting device is equipped with a storage battery as an emergency power source. In an emergency, the storage battery is used as a power source to turn on an emergency light source to ensure illumination. Usually, since the voltage for lighting the emergency light source is higher than the voltage of the storage battery, it is common to light the emergency light source using a booster circuit. In recent years, the use of LEDs as an emergency light source has increased, and by controlling to a constant output, a certain level of illuminance is ensured during the effective lighting period.

  Patent Document 1 discloses a technique for preventing overcurrent at the same time by controlling the forward current (IF) of the LED to be constant, providing a forward voltage (VF) overvoltage limiter, and controlling the switching operation. Yes.

JP 2006-085993 A

  When output constant power control is performed on the load LED of the emergency lighting device, the forward current IF increases when the forward voltage VF of the load LED decreases. Therefore, it is conceivable to provide an overcurrent limiter to prevent an excessive increase in the forward current IF. However, when the voltage (input voltage) of the storage battery provided as an emergency power supply decreases, the inflow (input) current from the storage battery increases and the heat generation of the circuit components such as the converter circuit increases. was there.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an emergency lighting device that can prevent the heat generation of circuit components from increasing when the input voltage from the storage battery decreases. And

  An emergency lighting device according to the present invention includes an input voltage detection circuit that detects an input voltage, a DCDC converter circuit that transforms the input voltage and applies it to a load, and detects a forward voltage and a forward current of the load. A control circuit that controls the DCDC converter circuit so that the load is controlled at a constant power, and a limiter that suppresses an increase in the forward current when the forward voltage falls below a predetermined overcurrent limiter threshold. And the limiter circuit increases the overcurrent limiter threshold when the input voltage detection circuit detects that the input voltage has decreased to a predetermined value. .

  According to the present invention, when the input voltage from the storage battery decreases, an increase in the forward current IF of the load is prevented, so that the heat generation of the circuit components can be suppressed.

It is a circuit diagram of the emergency lighting device according to the embodiment. It is a graph which shows the connection point electric potential of a 3rd resistive element, and the relationship of forward current. It is a figure which shows changing an overcurrent limiter threshold value when an input voltage falls. It is a simplified diagram of an emergency lighting device according to an embodiment. It is a simplified diagram of an emergency lighting device according to a comparative example.

  An emergency lighting device according to an embodiment of the present invention will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and repeated description may be omitted.

Embodiment.
FIG. 1 is a circuit diagram of an emergency lighting device according to an embodiment. The voltage of the storage battery 101 is Vbat, which is the input voltage of the emergency lighting device. An input voltage detection circuit 102 that detects an input voltage is connected to the storage battery 101. The input voltage detection circuit 102 includes two first resistance elements R1 and R2 that divide the input voltage. The input voltage detection circuit 102 includes a diode D1 having a cathode connected to a connection point between the two first resistance elements R1 and R2 connected in series. The anode of the diode D1 is connected to the resistance element R3.

Connected to the storage battery 101 is a DCDC converter circuit 201 that transforms an input voltage and applies it to a load 401 composed of an LED module in which a plurality of LEDs are connected in series. The LEDs may be connected not in series but in series and parallel. The DCDC converter circuit 201 is composed of a booster circuit. The DCDC converter circuit 201 is controlled by turning on and off the switching element Q1 by a drive signal from a control circuit 202 connected to the DCDC converter circuit 201. The control circuit 202 controls the switching element Q1 of the DCDC converter circuit 201 so that the load 401 is controlled with constant power. The control circuit 202 is also referred to as a CPU (Central Processing Unit, a central processing unit, a processing unit, a processing unit, a microprocessor, a microcomputer, a processor, and a DSP that executes a program stored in a memory even if it is dedicated hardware. ).
The DCDC converter circuit 201 includes the aforementioned switching element Q1, inductor Id, diode Dd, and capacitor Cd. The drain of the switching element Q1 is connected between the inductor Id and the anode of the diode Dd. When the switching element Q1 is turned on, energy is stored in the inductor Id. When the switching element Q1 is turned off, the capacitor Cd is charged by the energy of the inductor Id.

  The electric power generated by the DCDC converter circuit 201 is applied to the load 401. The forward voltage of the load 401 is VF, and the forward current is IF. A limiter circuit 301 is connected to the capacitor Cd of the DCDC converter circuit 201. The limiter circuit 301 is a circuit that suppresses an increase in the forward current IF when the forward voltage VF becomes equal to or lower than a predetermined value (overcurrent limiter threshold).

  The limiter circuit 301 includes a base bias resistor R8, an NPN transistor Q2, a shunt regulator IC2, and two second resistor elements R4 and R5 connected in series. A connection point between the collector of the NPN transistor Q2 of the limiter circuit 301 and the base bias resistor R8 is connected to the positive electrode of the capacitor Cd of the DCDC converter circuit 201. The cathode of the shunt regulator IC2 is connected to the base of the NPN transistor Q2. The anode of the diode D1 is connected to the connection point between the second resistance elements R4 and R5 and the reference of the shunt regulator IC2 via the resistance element R3. A second resistance element R4 is connected to the emitter of the NPN transistor Q2. The base bias resistor R8 is connected between the connection point of the base of the NPN transistor Q2 and the cathode of the shunt regulator IC2 and the collector of the NPN transistor Q2.

  Two third resistance elements R6 and R7 connected in series are connected to the load 401 in parallel. The emitter of the NPN transistor Q2 is connected to the connection point between the two third resistance elements R6 and R7. The control circuit 202 includes an FB (Feed Back) terminal. The FB terminal is connected to the cathode side of the LED constituting the load 401. Therefore, the control circuit 202 can detect the forward voltage VF and the forward current IF of the load 401 via the FB terminal. A current detection resistor R9 of the load 401 is connected to the cathode of the LED, and a current input resistor R10 and a current / voltage input resistor R11 are connected in series between the connection point of the cathode and the current detection resistor R9 and the FB terminal. Yes.

  Next, the operation of the emergency lighting device will be described. The DCDC converter circuit 201 (switching circuit) transforms the voltage Vbat of the storage battery 101 into a forward voltage VF necessary for lighting the load 401. The forward voltage VF and the forward current IF applied to the load 401 are added and fed back to the control circuit 202 to realize constant power control. In addition, you may implement | achieve the constant power control which used the forward voltage VF and the forward current IF of the load 401 as multiplication feedback by another method. In this way, the load 401 is subjected to constant power control.

  The limiter circuit 301 is connected to the feedback route of the forward voltage VF before the addition or multiplication. The limiter circuit 301 is a circuit that prevents the forward current IF from excessively rising when the forward voltage VF decreases.

  The limiter circuit 301 operates so as to keep the forward current below a certain threshold when the forward voltage VF decreases due to a temperature change or the like. For example, the cathode voltage Vk of the limiter circuit 301 is set to 10V, and the base-emitter voltage Vbe of the NPN transistor Q2 is set to 0.6V.

The operation of the limiter circuit 301 will be described.
1. When forward voltage VF of load 401 is larger than a predetermined value, Vk−Vbe = 10−0.6 = 9.4 V is referred to as overcurrent limiter threshold value 1. When the connection point potential of the third resistance elements R6 and R7 exceeds the overcurrent limiter threshold 1, the connection point potential of the second resistance elements R4 and R5 exceeds the reference voltage of the shunt regulator IC2, and the shunt regulator IC2 Tries to lower the connection point potential of the third resistance elements R6 and R7. However, since the transistor Q2 is an NPN transistor, the current cannot be sucked through the third resistance element R6, so that the connection point potential of the third resistance elements R6 and R7 cannot be lowered. Therefore, when the forward voltage VF of the load 401 is larger than a predetermined value, that is, when the connection point potential of the third resistance elements R6 and R7 exceeds the overcurrent limiter threshold 1, the FB terminal of the control circuit 202 The signal obtained by adding the forward voltage VF and the forward current IF is fed back, and constant power control is executed.

  FIG. 2 is a graph showing the relationship between the connection point potential of the third resistance elements R6 and R7 and the forward current IF. As described above, when the connection point potential of the third resistance elements R6 and R7 exceeds the overcurrent limiter threshold 1, the constant power control indicated by the solid line in FIG. 2 is realized.

2. When the forward voltage VF of the load 401 is equal to or lower than a predetermined value On the other hand, when the connection point potential of the third resistance elements R6 and R7 is Vk−Vbe = 9.4V (overcurrent limiter threshold 1) or lower, The connection point potential of the two-resistance elements R4 and R5 is less than the reference voltage of the shunt regulator IC2. Therefore, the shunt regulator IC2 constantly controls the connection point potential of the third resistance elements R6 and R7 so as to maintain the value of 9.4V in order to maintain the reference voltage. Even if the forward voltage VF continues to decrease, the forward current IF does not increase because the node potential of the third resistance elements R6 and R7 is constant.

  Therefore, when the connection point potential of the third resistance elements R6 and R7 becomes equal to or lower than the overcurrent limiter threshold value 1, the overcurrent suppression control indicated by the one-dot chain line in FIG. As described above, the limiter circuit 301 can suppress an increase in the forward current IF when the forward voltage VF of the load 401 decreases.

  The emergency lighting device according to the embodiment of the present invention suppresses the forward current IF from becoming an overcurrent when the voltage Vbat (input voltage) of the storage battery 101 decreases while assuming the operation of the limiter circuit 301 described above. To do. Specifically, the limiter circuit 301 increases the overcurrent limiter threshold when the input voltage Vbat detection circuit 102 detects that the input voltage Vbat has decreased to a predetermined value. This will be described in detail.

  FIG. 3 is a diagram illustrating changing the overcurrent limiter threshold when the input voltage Vbat decreases. At the time indicated by circle 1, the connection point potential of the third resistance elements R6 and R7 is larger than the overcurrent limiter threshold value 1, and the load 401 is controlled with constant power. When the input voltage Vbat of the storage battery 101 drops to the threshold value of the input voltage detection circuit 102, the overcurrent limiter threshold value 1 of the limiter circuit 301 is changed to the overcurrent limiter threshold value 2. That is, the transition from circle 1 to circle 2 is made. Thereby, it is suppressed that the forward voltage VF becomes an overcurrent at a high value.

  For example, it is assumed that the discharge reference voltage is 6.6 V, R1 is 22 kΩ, R2 is 3.0 kΩ, VF of D1 is 0.6 V, and the reference voltage Vref of the shunt regulator IC2 is 1.25 V.

A. When the voltage Vbat (input voltage) of the storage battery 101 is high (Vbat> 5.4 V)
When Vbat * R2 / (R1 + R2)> 0.65V, the diode D1 is non-conductive and the forward voltage VF is controlled by the voltage set by the second resistance elements R4 and R5, and the forward voltage VF and the forward current IF are controlled. The constant power is controlled by the addition feedback. This control is the same as the control when the connection point potential of the third resistance elements R6 and R7 exceeds the overcurrent limiter threshold value 1 described above.

B. When the voltage Vbat (input voltage) of the storage battery 101 is low (Vbat ≦ 5.4V)
When Vbat * R2 / (R1 + R2) ≦ 0.65, the diode D1 becomes conductive, and the connection point potential of the third resistance elements R6 and R7 increases by the amount that the connection point voltage of the second resistance elements R4 and R5 decreases. . When the connection point potential of the third resistance elements R6 and R7 rises, the control circuit 202 recognizes that the forward voltage VF has risen, and the forward current IF decreases by constant power control.

  As long as the input voltage from the storage battery 101 is low and the diode D1 is conductive, the forward increase of the forward voltage VF is maintained, so that the forward current IF is kept at a low value by constant power control. This is equivalent to changing the overcurrent limiter threshold 1 to an overcurrent limiter threshold 2 that is higher than the overcurrent limiter threshold 1 in FIG.

  As described above, the forward current IF when the overcurrent limiter threshold is changed by the input voltage detection circuit 102 is smaller than the forward current IF when the input voltage detection circuit 102 is not provided. By limiting to a small current value, the inflow (input) current from the storage battery 101 is reduced, and an increase in heat generation of the circuit components can be suppressed.

  By the way, when the limiter circuit 301 and the input voltage detection circuit 102 are not provided, the forward voltage VF decreases because the temperature of the LED load increases due to self-heating at the end of discharge of the voltage Vbat of the storage battery 101. In the case of the output constant power control, when the forward voltage VF decreases, the forward current IF increases and the temperature of the DCDC converter circuit 201 increases. In addition, in the constant power control at the end of discharge of the voltage Vbat of the storage battery 101, the inflow (input) current from the storage battery 101 to the DCDC converter circuit 201 is increased by the amount of the decrease in the voltage Vbat of the storage battery 101. The temperature will rise. For these two reasons, the temperature of the DCDC converter circuit 201 rises at the end of discharge of the storage battery 101.

  However, according to the emergency lighting device according to the embodiment of the present invention, the input voltage detection circuit 102 and the limiter circuit 301 for preventing overcurrent are used in combination as described above, so that a circuit such as the DCDC converter circuit 201 is used. The temperature rise of parts can be suppressed. Specifically, the following merits can be obtained.

a When the voltage Vbat of the storage battery 101 and the forward voltage VF of the load 401 are lowered, an excessive temperature rise can be suppressed.
b Inflow (input) current from the storage battery 101 to the circuit can be suppressed.
c The input voltage detection circuit 102 can be configured with a small number of parts. By combining the limiter circuit 301 and the input voltage detection circuit 102, the threshold value of the limiter circuit 301 and the forward direction controlled by the limiter circuit 301 are set by setting constants of the first resistance elements R1, R2 and the second resistance elements R4, R5. The current IF can be easily adjusted.
d In order to reduce the output when the voltage Vbat of the storage battery 101 is lowered, when the voltage Vbat rises at the time of power-on or the like, the operation gradually increases. That is, it becomes a soft start.
e Even if the voltage Vbat of the storage battery 101 decreases and the forward current IF is limited by the limiter circuit 301, the load 401 is not completely extinguished, so that the evacuation induction time can be extended.
f Since the circuit is not stopped by the protective operation of the limiter circuit 301, there is no possibility that the load 401 is extinguished by a malfunction of the protective circuit.

  FIG. 4 is a simplified diagram of an emergency lighting device according to an embodiment of the present invention. An input voltage detection circuit 102 that detects the voltage of the storage battery 101 is provided. By detecting the voltage Vbat of the storage battery 101 at a certain voltage below the discharge reference voltage and changing the overcurrent limiter threshold of the limiter circuit 301, the forward current IF is limited even if the forward voltage VF does not decrease, and the inflow (Input) The current is reduced to suppress thermal stress on the circuit components of the DCDC converter circuit 201.

  FIG. 5 is a simplified diagram of an emergency lighting device according to a comparative example. The emergency lighting device of the comparative example does not have an input voltage detection circuit. In this case, the power on the output side can be suppressed to some extent, but because of constant power control, when the voltage Vbat of the storage battery 101 decreases, the inflow (input) current from the storage battery 101 increases, and the circuit of the DCDC converter circuit 201 Heat generation of parts will increase. The technical standard stipulates that the emergency lighting device must be lit for a certain period of time until the voltage of the storage battery decreases to a certain threshold value (discharge reference voltage) in an emergency (such as a power failure). If lighting can be continued up to the discharge reference voltage, it does not need to be turned on thereafter. Excessive DCDC converter circuit operation below the discharge reference voltage causes thermal stress on the DCDC converter circuit.

  In the comparative example, when the voltage of the storage battery 101 decreases, the inflow (input) current from the storage battery 101 increases due to the output constant power control, and the heat generation of the circuit components increases. However, according to the emergency lighting device according to the embodiment of the present invention, by adding the input voltage detection circuit 102 that detects the voltage drop of the storage battery 101, the overcurrent limiter threshold of the limiter circuit 301 is changed to change the storage battery 101. Since the inflow (input) current from is limited, an increase in heat generation can be suppressed.

  The emergency lighting device according to the embodiment of the present invention can be variously modified within a range not losing its characteristics.

  DESCRIPTION OF SYMBOLS 101 Storage battery, 102 Input voltage detection circuit, 201 DCDC converter circuit, 202 Control circuit, 301 Limiter circuit, 401 Load

Claims (4)

An input voltage detection circuit for detecting the input voltage;
A DCDC converter circuit that transforms the input voltage and applies it to a load;
A control circuit that detects the forward voltage and forward current of the load and controls the DCDC converter circuit so that the load is controlled at a constant power;
A limiter circuit that suppresses an increase in the forward current when the forward voltage is equal to or lower than a predetermined overcurrent limiter threshold,
The emergency lighting device, wherein the limiter circuit increases the overcurrent limiter threshold when the input voltage detection circuit detects that the input voltage has decreased to a predetermined value. The input voltage detection circuit is
Two first resistance elements for dividing the input voltage;
A diode having a cathode connected to a connection point of the two first resistance elements,
2. The emergency lighting device according to claim 1, wherein an anode of the diode is connected to the limiter circuit. The limiter circuit is
An NPN transistor;
A shunt regulator having a cathode connected to the base of the NPN transistor;
Two second resistance elements connected to the emitter of the NPN transistor,
The emergency lighting device according to claim 2, wherein the anode of the diode is connected to a connection point between the connection point of the two second resistance elements and a reference of the shunt regulator. Two third resistance elements connected in parallel to the load;
The emergency lighting device according to claim 3, wherein an emitter of the NPN transistor is connected to a connection point of the two third resistance elements.

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