JP6273642B2 - LED lighting device - Google Patents

Description

  The present invention relates to an LED lighting device for lighting an LED load.

  As a conventional example, a power supply device described in Patent Document 1 is illustrated. This conventional example includes a constant voltage unit that is supplied with power from an AC power source and outputs a constant voltage, and a constant current unit that receives a voltage from the constant voltage unit and drives a lighting load (for example, an LED load) to light.

  The constant current unit includes a voltage detection unit and a setting unit. The voltage detection unit detects an input voltage supplied from the constant voltage unit after the voltage supply by the constant voltage unit is started. The setting unit sets an operation start voltage at which the constant current unit starts operating, and changes the operation start voltage in response to a detection result by the voltage detection unit.

  In this conventional example, the current peak value when the voltage is supplied from the constant voltage unit and the constant current unit starts operation can be arbitrarily set, so that the current peak value at the start can be controlled. The stress on the circuit elements of the unit can be reduced.

JP 2011-205855 A

  Incidentally, in the conventional example described in Patent Document 1, the constant current unit is configured by a high-side step-down chopper circuit. When the rated voltage of the LED load is relatively high, an instantaneous voltage drop (instantaneous voltage drop) occurs in the AC power supply in approximately less than 1 second, and the output voltage of the constant voltage unit is below the rated voltage of the LED load. May fall. When the output voltage of the constant voltage unit drops below the rated voltage of the LED load in this way, the switching element of the constant current unit (step-down chopper circuit) cannot be driven, and the LED load may remain off.

  The present invention has been made in view of the above problems, and an object thereof is to normally light an LED load even when an instantaneous voltage drop occurs.

  The LED lighting device of the present invention includes a DC power supply unit that boosts an input voltage to a desired DC voltage, a step-down chopper unit that steps down a DC input voltage supplied from the DC power supply unit and applies it to an LED load, and the DC A control block for controlling the operation of the power supply unit and the step-down chopper unit, the DC power supply unit includes a step-up chopper circuit having a first semiconductor switching element, and the step-down chopper unit intermittently connects the DC input voltage. A second semiconductor switching element that conducts energy stored when the DC input voltage is applied via the second semiconductor switching element, and an inductor that releases energy stored when the DC input voltage is not applied. And the second semiconductor switching element is connected to a higher potential side than the inductor with respect to the DC input voltage. The control block includes a first control unit that performs switching control of the first semiconductor switching element according to a predetermined first sequence, and a second control unit that performs switching control of the second semiconductor switching element according to a predetermined second sequence; A sequence circuit unit configured to cause the first control unit to start the first sequence and to cause the second control unit to start the second sequence; and to measure a predetermined threshold by measuring the DC input voltage. A voltage detection unit that outputs a voltage drop signal when the measured value falls below the threshold value, and the sequence circuit unit receives the voltage drop signal from the voltage detection unit. The first control unit and the second control unit are configured to start the first sequence and the second sequence from the beginning. And butterflies.

  In this LED lighting device, it is preferable that the threshold value of the voltage detection unit is set to a value that is 80% of a steady-state voltage value of the DC input voltage.

In this LED lighting device, it is preferable that the steady-state voltage value of the DC input voltage is lower than twice the rated voltage of the LED load.
In the LED lighting device, the first sequence means that the control block feedback-controls the on-duty ratio of the first semiconductor switching element of the boost chopper circuit to make the DC input voltage a predetermined constant voltage. It is preferable that this is a series of operations.
In the LED lighting device, the second sequence refers to switching control of the second semiconductor switching element in a discontinuous mode in which an inductor current flowing through the inductor is discontinuous according to a dimming signal input from the outside. It is preferable that this is a series of operations.

  In the LED lighting device of the present invention, when an instantaneous voltage drop occurs, the sequence circuit unit resets the first sequence of the first control unit and the second sequence of the second control unit and executes them from the beginning. Even if this occurs, the LED load can be normally lit.

It is a time chart for demonstrating the operation | movement at the time of the instantaneous voltage drop generation | occurrence | production in Embodiment 1 of the LED lighting device which concerns on this invention. It is a circuit diagram same as the above. It is a time chart for demonstrating the basic operation | movement in the same as the above. It is a time chart for demonstrating the basic operation | movement in a comparative example same as the above. It is a time chart for demonstrating the operation | movement at the time of the instantaneous voltage drop generation | occurrence | production in the comparative example same as the above. It is a time chart for demonstrating the basic operation | movement in Embodiment 2 of the LED lighting device which concerns on this invention. It is a time chart for demonstrating the operation | movement at the time of the instantaneous voltage drop generation | occurrence | production in the same as the above.

  Hereinafter, embodiments of an LED lighting device according to the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 2, the LED lighting device of this embodiment includes a step-down chopper unit 1, a control block 2, and a DC power supply unit 3.

  The DC power supply unit 3 is configured to convert (boost) an AC voltage supplied from a commercial AC power supply 4 into a desired DC voltage. The DC power supply unit 3 includes a filter unit 30, a rectifier circuit 31, a PFC (Power Factor Correction) unit 32, and a smoothing capacitor C1. The filter unit 30 removes harmonic noise superimposed on the AC voltage / AC current input from the AC power supply 4 and harmonic noise generated in the PFC unit 32. The rectifier circuit 31 is formed of a diode bridge, and full-wave rectifies the AC voltage / AC current supplied from the AC power supply 4. The PFC unit 32 is a conventionally known step-up chopper circuit having a semiconductor switching element (first semiconductor switching element). The PFC unit 32 boosts the pulsating voltage that has been full-wave rectified by the rectifier circuit 31 to a desired DC voltage. To improve the rate. The smoothing capacitor C1 smoothes the output voltage of the PFC unit 32. In the following description, a DC voltage input from the DC power supply unit 3 to the step-down chopper unit 1 is referred to as a DC input voltage VDC.

  The step-down chopper unit 1 includes a semiconductor switching element (second semiconductor switching element) Q1 made of a field effect transistor, an inductor T1, a diode D1, a capacitor C2, a detection resistor R1, resistors R2 and R9, and the like. A series circuit of the semiconductor switching element Q 1, the inductor T 1, the capacitor C 2, and the detection resistor R 1 is connected between the output terminals of the DC power supply unit 3. The cathode of the diode D1 is connected to the connection point between the semiconductor switching element Q1 and the inductor T1, and the anode of the diode D1 is connected to the connection point between the detection resistor R1 and the resistor R9. The resistor R9 is connected in parallel with the diode D1, and one end of the resistor R2 is connected to the gate of the semiconductor switching element Q1. The LED load 5 is connected to both ends of the capacitor C2.

  The LED load 5 is, for example, a straight tube LED lamp standardized by the Japan Electric Bulb Industry Association standard JEL801 “Straight tube LED lamp system with L-shaped pin cap GX16t-5 (for general lighting)”. When the straight tube LED lamp is used as the LED load 5, the LED load 5 is detachably connected between the output ends (both ends of the capacitor C2) of the step-down chopper unit 1 using a lamp socket or a connector (not shown).

  Note that the step-down chopper unit 1 is configured as a so-called high side type in which the semiconductor switching element Q1 is connected to a higher potential side than the inductor T1. This is because the input voltage of the step-down chopper section 1 is defined as 300 volts or less in the Japan Electric Bulb Industry Association Standard JEL801 “Straight-tube LED lamp system with L-shaped pin cap GX16t-5 (for general lighting)”. is there. That is, when the semiconductor switching element Q1 of the step-down chopper unit 1 is connected to a lower potential side than the inductor T1 (low-side type), the input voltage of the step-down chopper unit 1 exceeds 300 volts.

  The control block 2 includes a control IC 20 made up of a high voltage integrated circuit, an external circuit element, and a control power generation unit 29.

  The control power supply generation unit 29 includes a switching power supply circuit and generates a control power supply Vcc from the DC input voltage VDC.

  The control IC 20 includes a step-down control unit 21, a high-side driver unit 22, an operational amplifier 23, a switch 24, a sequence circuit unit 25, a PFC control unit 26, a DC input voltage detection unit (hereinafter referred to as a VDC detection unit) 27, and a control. An optical unit 28, voltage dividing resistors R3, R4, and the like are provided. The control IC 20 has a CS terminal, ZCD terminal, OP + terminal, OP- terminal, OPout terminal, Ho terminal, HGND terminal, HVcc terminal, Vcc terminal, Do terminal, GND terminal, VDCin terminal, CTA terminal, Dimsig terminal, Terminals such as Vdim terminal and PWMin terminal are provided.

  The sequence circuit unit 25 generates a triangular wave voltage (hereinafter referred to as a CTA terminal voltage) having a constant period To (for example, 50 milliseconds) by charging and discharging a capacitor C5 externally attached to the CTA terminal. The time is counted by counting the period To of the CTA terminal voltage. Further, the sequence circuit unit 25, when the elapsed time from when the AC power supply 4 is turned on (hereinafter referred to as the power-on time) reaches the first operation start time (for example, 0.5 seconds), The first operation start signal S1 is output to the step-down controller 21 (high level). Further, the sequence circuit unit 25 outputs the second operation start signal S2 to the dimming unit 28 (high level) when the elapsed time reaches the second operation start time (for example, 0.7 seconds). Further, the sequence circuit unit 25 outputs a third operation start signal S3 to the VDC detection unit 27 (sets to high level) when the elapsed time reaches a third operation start time (for example, 0.8 seconds).

  When the first operation start signal S1 is output from the sequence circuit unit 25, the PFC control unit 26 outputs a drive signal from the Do terminal, and the first semiconductor switching element (not shown) constituting the PFC unit 32 is output. Control switching. Further, the PFC control unit 26 feedback-controls the on-duty ratio of the first semiconductor switching element of the PFC unit 32 so that the output voltage (DC input voltage VDC) of the DC power supply unit 3 is set to a predetermined constant voltage. Composed. Here, the PFC control unit 26 outputs a drive signal from the Do terminal to control the switching of the first semiconductor switching element, and outputs a constant DC voltage VDC by feedback controlling the on-duty ratio of the first semiconductor switching element. A series of operations is referred to as a first sequence. However, since such a PFC control unit 26 is well known in the art, a detailed configuration and operation illustration and description are omitted.

  The high-side driver unit 22 drives the semiconductor switching element Q1 of the step-down chopper unit 1, and outputs a drive signal from the Ho terminal to the gate of the semiconductor switching element Q1 using the voltage supplied from the HVcc terminal. Configured as follows. Note that a bootstrap circuit for boosting the control voltage Vcc is externally attached to the HVcc terminal. The bootstrap circuit includes a capacitor C3 connected between the HGND terminal and the HVcc terminal, and a diode D2 having an anode connected to the Vcc terminal to which the control power supply Vcc is input and a cathode connected to the HVcc terminal. . In other words, the bootstrap circuit charges the capacitor C3 through the path of the control power generation unit 29 from the diode D2, the capacitor C3, and the resistor R9 of the step-down chopper unit 1, and is higher than the control power supply voltage Vcc by the charging voltage of the capacitor C3. Is input to the HVcc terminal.

  In the operational amplifier 23, the reference voltage Vs is input to the non-inverting input terminal (OP + terminal), the voltage across the detection resistor R1 is input to the inverting input terminal (OP- terminal), and the output terminal (OPout terminal) and the inverting input terminal A parallel circuit of a feedback resistor R2 and a capacitor C4 is connected between them. The reference voltage Vs is a voltage obtained by dividing the output voltage of the dimmer 28 (terminal voltage of the Dimsig terminal) by the voltage dividing resistors R5 and R6 as described later, and changes in accordance with the output voltage of the dimmer 28. To do. The voltage across the detection resistor R1 (hereinafter referred to as the detection voltage Vx) is a voltage proportional to the output current Io of the step-down chopper unit 1. The detection voltage Vx is integrated by an integrating circuit of an external feedback resistor R2 and a capacitor C4.

  Thus, an inverting amplifier circuit is configured by the operational amplifier 23 and the parallel circuit of the feedback resistor R2 and the capacitor C4. This inverting amplifier circuit inverts and amplifies the difference between the integrated value of the detection voltage Vx and the reference voltage Vs and applies it to the series circuit of the voltage dividing resistors R3 and R4. One end of the series circuit of the voltage dividing resistors R3 and R4 is connected to the output terminal of the operational amplifier 23, and the other end is connected to the ground via the GND terminal. Then, the voltage divided by the voltage dividing resistors R3 and R4 is input to the step-down control unit 21 as the threshold voltage X1. The operational amplifier 23 is applied with the control power supply voltage Vcc through the switch 24, operates when the switch 24 is on, and stops when the switch 24 is off. .

  The VDC detection unit 27 takes in the voltage across the detection resistor R10 connected to the output terminal on the high potential side of the DC power supply unit 3 from the VDCin terminal and takes the voltage across the both ends (measured value of the DC input voltage VDC) with a predetermined threshold. Compared with a value, a voltage drop signal is output when the measured value falls below the threshold value. Here, the threshold value is preferably set to a value of 80% of a steady-state voltage value (for example, a rated value) of the DC input voltage VDC. The VDC detection unit 27 is configured to operate when the third operation start signal S3 is output from the sequence circuit unit 25 and to output a voltage drop signal to the sequence circuit unit 25.

  The dimming unit 28 converts a dimming signal (a PWM signal made up of a rectangular wave having a fixed period) input from the outside to the PWMin terminal into a DC voltage, and the converted DC voltage (hereinafter referred to as a dimming output voltage). ) Is output from the Dimsig terminal. The dimmer 28 takes in a voltage obtained by dividing the control power supply voltage Vcc by the voltage dividing resistors R7 and R8 from the VDim terminal. Then, the dimming unit 28 determines the voltage value of the dimming output voltage with respect to the lower limit value of the dimming level indicated by the on-duty ratio of the dimming signal, corresponding to the divided voltage.

  As already described, the series circuit of the voltage dividing resistors R5 and R6 and the capacitor C6 are connected in parallel between the Dimsig terminal and the ground. A voltage obtained by dividing the dimming output voltage output from the Dimsig terminal by the voltage dividing resistors R5 and R6 is input from the OP + terminal to the non-inverting terminal of the operational amplifier 23 as the reference voltage Vs. The capacitor C6 forms an integrating circuit with the voltage dividing resistors R5 and R6, and plays a role of fading the change in the divided voltage.

  The dimming unit 28 sets the dimming output voltage to a voltage equal to the voltage applied to the VDim terminal until the second operation start signal S2 is input from the sequence circuit unit 25. Then, the dimming unit 28 starts operating when the second operation start signal S2 is input, converts the dimming signal input from the PWMin terminal into a DC dimming output voltage, and outputs the DC dimming output voltage from the Dimsig terminal.

  The step-down control unit 21 includes a timer and a comparator (both not shown) that count a certain period, and raises a control signal output to the high-side driver unit 22 to a high level at a period counted by the timer. When the control signal rises to a high level, the high side driver unit 22 raises the terminal voltage of the Ho terminal to a high level and turns on the second semiconductor switching element Q1.

  When the second semiconductor switching element Q1 is turned on, the step-down chopper circuit 1 starts to operate, the output current Io (inductor current IL) gradually increases, and the detection voltage Vx also increases as the output current Io increases. The step-down control unit 21 compares the threshold voltage X1 obtained by dividing the output voltage of the operational amplifier 23 by the voltage dividing resistors R3 and R4 with the detection voltage Vx input from the CS terminal by a comparator (not shown). When the detection voltage Vx exceeds the threshold voltage X1, the control signal falls to the low level. When the control signal falls to the low level, the high side driver unit 22 lowers the terminal voltage of the Ho terminal to the low level and turns off the second semiconductor switching element Q1.

  When the second semiconductor switching element Q1 is turned off, the energy accumulated in the inductor T1 is released and a regenerative current (inductor current IL) flows. However, this regenerative current (inductor current IL) gradually decreases with time. Then, after the regenerative current (inductor current IL) becomes zero, the step-down control unit 21 raises the control signal to a high level at the timing when the timer counts the period. In addition, in synchronization with the rise of the control signal, the high side driver unit 22 turns on the second switching element Q1. As a result, the LED load 5 is turned on when the DC output voltage Vo of the step-down chopper unit 1 is applied. Further, the step-down control unit 21 changes the timing at which the second switching element Q1 is turned off in accordance with the dimming signal (dimming output voltage). Therefore, the LED load 5 is dimmed when the DC output voltage Vo of the step-down chopper unit 1 increases or decreases in response to the dimming signal. Note that the operation mode of the step-down control unit 21 in the present embodiment is a discontinuous mode in which the inductor current IL flowing through the inductor T1 is discontinuous. Here, a series of operations in which the step-down control unit 21 outputs a control signal to the high-side driver unit 22 and performs switching control of the second semiconductor switching element Q1 of the step-down chopper unit 1 in the discontinuous mode is referred to as a second sequence.

Next, operation | movement of the LED lighting device of this embodiment is demonstrated.
(1) Basic Operation First, the basic operation will be described with reference to the time chart of FIG.

  When the AC power supply 4 is turned on, a DC input voltage VDC that has been full-wave rectified by the rectifier circuit 31 and passed through the PFC unit 32 and smoothed by the smoothing capacitor C1 is input to the control power generation unit 29. Then, the control power supply generation unit 29 generates a control power supply from the time point when the DC input voltage VDC is input (time t = t0, hereinafter referred to as a power-on time point) and supplies it to each unit.

  When the control power supply voltage Vcc rises, the sequence circuit unit 25 starts operating. The sequence circuit unit 25 counts the cycle To of the CTA terminal voltage, and when the first operation start time (for example, 0.5 seconds) has elapsed since the power was turned on, the first operation start signal S1 is made high. Launch to level.

  When the first operation start signal S1 rises to a high level, the PFC control unit 26 starts the first sequence and controls the switching of the first semiconductor switching element. As a result, the DC input voltage VDC input from the DC power supply unit 3 to the step-down chopper unit 1 starts to rise and stabilizes to a predetermined value (rated value) while causing ringing due to load fluctuation.

  Further, the switch 24 is turned on when the first operation start signal S1 rises to a high level, and the operational amplifier 23 operates when the control power supply voltage Vcc is supplied. Further, when the first operation start signal S1 rises to a high level, the step-down control unit 21 starts the second sequence to control the switching of the second semiconductor switching element Q1, and the initial dimming output voltage (= VDim terminal terminal) The output current Io determined by the voltage is operated to flow through the LED load 5.

  The sequence circuit unit 25 raises the second operation start signal S2 to a high level when a second operation start time (for example, 0.7 seconds) has elapsed since the power-on (time t = t2).

  The dimmer 28 starts operating when the second operation start signal S2 rises to a high level, converts the dimming signal input from the PWMin terminal into a DC dimming output voltage, and outputs it from the Dimsig terminal. However, the dimming output voltage gradually increases from the initial value due to the influence of the capacitor C6, and finally becomes a voltage corresponding to the dimming signal.

  The step-down control unit 21 changes the timing to turn off the second switching element Q1 according to the dimming output voltage, gradually increases the output current Io flowing from the step-down chopper unit 1 to the LED load 5, and finally dimming The current value corresponding to the signal is stabilized.

  Further, the sequence circuit unit 25 raises the third operation start signal S3 to a high level when a third operation start time (for example, 0.8 seconds) elapses from the time of power-on (time t = t3). The VDC detection unit 27 starts operation when the third operation start signal S3 rises to a high level, takes in the voltage across the detection resistor R10 from the VDCin terminal, and compares it with a threshold value. The VDC detection unit 27 does not operate during a period (t3-t0) from when the power is turned on until the third operation start signal S3 elapses.

By supplying the output current Io corresponding to the dimming signal from the step-down chopper unit 1 as described above, the LED load 5 can be turned on (dimmed lighting).
(2) Operation when an instantaneous voltage drop occurs As shown in FIG. 1, it is assumed that an instantaneous voltage drop has occurred in the AC power supply 4 at time t = t4. When an instantaneous voltage drop occurs, the DC input voltage VDC input from the DC power supply unit 3 to the step-down chopper unit 1 also decreases. When the DC input voltage VDC falls below the threshold value of the VDC detection unit 27 (time t = t5), a voltage drop signal is output from the VDC detection unit 27 to the sequence circuit unit 25.

  Upon receiving the voltage drop signal from the VDC detection unit 27, the sequence circuit unit 25 stops outputting the first operation start signal S1, the second operation start signal S2, and the third operation start signal S3 (falls to a low level). . In addition, the sequence circuit unit 25 resets the count of the cycle To and restarts the count of the cycle To from the time when the voltage drop signal is received.

  When the first operation start signal S1 falls to a low level, the PFC control unit 26 stops the first sequence and turns off the first semiconductor switching element. Similarly, when the first operation start signal S1 falls to a low level, the step-down control unit 21 stops the second sequence and turns off the second semiconductor switching element Q1. As a result, the DC power supply unit 3 and the step-down chopper unit 1 both stop operating, and the LED load 5 is turned off.

Then, the sequence circuit unit 25 raises the first operation start signal S1 to the high level when the first operation start time has elapsed from the time when the voltage drop signal is received (time t = t6). When the first operation start signal S1 rises to the high level, the PFC control unit 26 starts the first sequence from the beginning. Similarly, the step-down control unit 21 starts the second sequence from the beginning when the first operation start signal S1 rises to a high level. As a result, both the DC power supply unit 3 and the step-down chopper unit 1 resume operation, and the LED load 5 is lit.
(3) Operation of comparative example when instantaneous voltage drop occurs (Part 1)
Here, in a comparative example in which an operation different from that of the LED lighting device of the present embodiment is performed, an operation when an instantaneous voltage drop occurs will be described with reference to a time chart shown in FIG.

  The comparative example illustrated here has a circuit configuration common to the LED lighting device of the present embodiment, but the operation of the sequence circuit unit 25 when an instantaneous voltage drop occurs is different.

  As shown in FIG. 4, it is assumed that an instantaneous voltage drop has occurred in the AC power supply 4 at time t = t4. When an instantaneous voltage drop occurs, the DC input voltage VDC input from the DC power supply unit 3 to the step-down chopper unit 1 also decreases. When the DC input voltage VDC falls below the threshold value of the VDC detection unit 27 (time t = t5), a voltage drop signal is output from the VDC detection unit 27 to the sequence circuit unit 25.

  When the sequence circuit unit 25 receives the voltage drop signal from the VDC detection unit 27, the second operation start signal S2 and the third operation start signal S3 are lowered to the low level, but the first operation start signal S1 remains at the high level. And

  The PFC control unit 26 continues the first sequence because the first operation start signal S1 is maintained at the high level. Similarly, the step-down control unit 21 continues the second sequence because the first operation start signal S1 is maintained at the high level. Therefore, the DC power supply unit 3 and the step-down chopper unit 1 also operate continuously without stopping.

Here, when the rated voltage of the LED load 5 is relatively low, even if the DC input voltage VDC further decreases after the instantaneous voltage drop, the DC input voltage VDC does not decrease to the rated voltage of the LED load 5. The terminal voltage is kept high. As a result, the high side driver unit 22 can switch the second semiconductor switching element Q1.
(4) Operation of comparative example when instantaneous voltage drop occurs (Part 2)
However, when the rated voltage of the LED load 5 is relatively high, the DC input voltage VDC may drop to the rated voltage of the LED load 5 after the instantaneous voltage drop as shown in FIG. 5 (VDC1 = Vo1). When the DC input voltage VDC becomes equal to the rated voltage of the LED load 5, the drive signal output from the high side driver unit 22 to the second semiconductor switching element Q1 is fixed at a high level. Then, since the capacitor C3 of the bootstrap circuit is not charged, the terminal voltage of the HVcc terminal is lowered and the second semiconductor switching element Q1 cannot be driven, and the LED load 5 is turned off.

  As described above, in the comparative example, when the LED load 5 having a relatively high rated voltage is connected to the step-down chopper unit 1, when the instantaneous voltage drop occurs, the step-down chopper unit 1 stops its operation and the LED load There is a risk that 5 will remain unlit.

  On the other hand, in the LED lighting device of the present embodiment, when an instantaneous voltage drop occurs, the sequence circuit unit 25 resets the first sequence of the PFC control unit 26 and the second sequence of the step-down control unit 21 and executes them from the beginning. For this reason, it is avoided that the drive signal of the high side driver unit 22 is fixed at a high level, so that the capacitor C3 of the bootstrap circuit is normally charged, and a decrease in the terminal voltage of the HVcc terminal can be suppressed. As a result, the LED load 5 can be prevented from remaining unlit after the instantaneous voltage drop.

  As described above, the LED lighting device according to the present embodiment boosts the input voltage to a desired DC voltage, and steps down the DC input voltage VDC supplied from the DC power supply unit 3 and applies it to the LED load 5. The step-down chopper unit 1 is provided. In addition, the LED lighting device according to the present embodiment includes a control block 2 that controls operations of the DC power supply unit 3 and the step-down chopper unit 1. The DC power supply unit 3 includes a boost chopper circuit having a first semiconductor switching element. The step-down chopper unit 1 includes a second semiconductor switching element Q1 that interrupts the DC input voltage VDC, and energy stored when the DC input voltage VDC is applied via the second semiconductor switching element Q1. And an inductor T1 that emits when not applied. Further, the step-down chopper unit 1 is configured such that the second semiconductor switching element Q1 is connected to a higher potential side than the inductor T1 with respect to the DC input voltage VDC.

  The control block 2 includes a first control unit (PFC control unit 26) that performs switching control of the first semiconductor switching element according to a predetermined first sequence, and a second control unit that performs switching control of the second semiconductor switching element Q1 according to a predetermined second sequence. And a control unit (step-down control unit 21). The control block 2 is a sequence circuit configured to cause the first control unit (PFC control unit 26) to start the first sequence and to cause the second control unit (step-down control unit 21) to start the second sequence. Part 25. Further, the control block 2 measures the DC input voltage VDC, compares it with a predetermined threshold value, and outputs a voltage drop signal when the measured value falls below the threshold value (VDC detection unit 27). Have

  When the sequence circuit unit 25 receives the voltage drop signal from the voltage detection unit (VDC detection unit 27), the first control unit (PFC control unit 26) and the second control unit (step-down control unit 21) receive the first sequence and The second sequence is configured to start from the beginning.

  The LED lighting device according to the present embodiment is configured as described above. When an instantaneous voltage drop occurs, the sequence circuit unit 25 resets the first sequence of the PFC control unit 26 and the second sequence of the step-down control unit 21 first. Run from. As a result, the LED lighting device of this embodiment can normally light the LED load 5 even if an instantaneous voltage drop occurs.

  Further, the threshold value of the voltage detection unit (VDC detection unit 27) is preferably set to a value that is 80% of the steady-state voltage value of the DC input voltage VDC.

  Further, the steady-state voltage value of the DC input voltage VDC is preferably lower than twice the rated voltage Vf of the LED load 5 (VDC <2 × Vf). For example, assuming that the rated voltage Vf of the LED load 5 is 210 volts, the steady-state voltage value of the DC input voltage VDC may be 410 volts, for example. At this time, the threshold value is 410 × 0.8 = 328 volts.

(Embodiment 2)
By the way, in the LED lighting device of the first embodiment, when an instantaneous voltage drop occurs and the first sequence of the PFC control unit 26 and the second sequence of the step-down control unit 21 are started from the beginning, the DC input voltage VDC is exceeded. The output voltage Vo may rise. As a result, the output voltage Vo becomes higher than the DC input voltage VDC, and the terminal voltage of the HVcc terminal is lowered, and the second semiconductor switching element Q1 may not be turned on.

  Therefore, the LED lighting device according to the present embodiment is prior to the second sequence when an instantaneous voltage drop occurs and the first sequence of the PFC control unit 26 and the second sequence of the step-down control unit 21 are started from the beginning. The first sequence is started. That is, the LED lighting device of the present embodiment has a circuit configuration common to the LED lighting device of Embodiment 1, but the operation of the sequence circuit unit 25 when an instantaneous voltage drop occurs is different.

  The sequence circuit unit 25 in this embodiment outputs a second operation start signal S2 to the step-down control unit 21 and the switch 24, and outputs a third operation start signal S3 to the dimming unit 28. There are features.

Next, operation | movement of the LED lighting device of this embodiment is demonstrated.
(1) Basic Operation First, the basic operation will be described with reference to the time chart of FIG.

  When the AC power supply 4 is turned on, a DC input voltage VDC that has been full-wave rectified by the rectifier circuit 31 and passed through the PFC unit 32 and smoothed by the smoothing capacitor C1 is input to the control power generation unit 29. Then, the control power supply generation unit 29 generates a control power supply from the time point when the DC input voltage VDC is input (time t = t0, hereinafter referred to as a power-on time point) and supplies it to each unit.

  When the control power supply voltage Vcc rises, the sequence circuit unit 25 starts operating. The sequence circuit unit 25 counts the cycle To of the CTA terminal voltage, and when the first operation start time (for example, 0.5 seconds) has elapsed since the power was turned on, the first operation start signal S1 is made high. Launch to level.

  When the first operation start signal S1 rises to a high level, the PFC control unit 26 starts the first sequence and controls the switching of the first semiconductor switching element. As a result, the DC input voltage VDC input from the DC power supply unit 3 to the step-down chopper unit 1 starts to rise and stabilizes to a predetermined value (rated value) while causing ringing due to load fluctuation.

  The sequence circuit unit 25 raises the second operation start signal S2 to a high level when a second operation start time (for example, 0.7 seconds) has elapsed since the power-on (time t = t2).

  The switch 24 is turned on when the second operation start signal S2 rises to a high level, and the operational amplifier 23 operates when the control power supply voltage Vcc is supplied. Further, when the second operation start signal S2 rises to a high level, the step-down control unit 21 starts the second sequence to control the switching of the second semiconductor switching element Q1, and the initial dimming output voltage (= VDim terminal terminal) The output current Io determined by the voltage is operated to flow through the LED load 5. At this time, since the PFC control unit 26 has started the first sequence first and the DC input voltage VDC has sufficiently increased, the output voltage Vo is prevented from becoming higher than the DC input voltage VDC.

  Further, the sequence circuit unit 25 raises the third operation start signal S3 to a high level when a third operation start time (for example, 0.8 seconds) elapses from the time of power-on (time t = t3). The VDC detection unit 27 starts operation when the third operation start signal S3 rises to a high level, takes in the voltage across the detection resistor R10 from the VDCin terminal, and compares it with a threshold value. The VDC detection unit 27 does not operate during a period (t3-t0) from when the power is turned on until the third operation start signal S3 elapses.

  The dimmer 28 starts operating when the third operation start signal S3 rises to a high level, converts the dimming signal input from the PWMin terminal into a DC dimming output voltage, and outputs it from the Dimsig terminal.

  The step-down control unit 21 changes the timing to turn off the second switching element Q1 according to the dimming output voltage, gradually increases the output current Io flowing from the step-down chopper unit 1 to the LED load 5, and finally dimming The current value corresponding to the signal is stabilized.

  By the way, when the step-down control unit 21 starts the second sequence at time t = t2 and the step-down chopper unit 1 starts operating, ringing starts to occur in the DC input voltage VDC. Then, when the VDC detection unit 27 starts operating at time t = t3, there is a possibility that the voltage drop signal is output from the VDC detection unit 27 because it falls below the threshold at the ringing valley of the DC input voltage VDC. However, even if a voltage drop signal is output from the VDC detection unit 27, the sequence circuit unit 25 stops the first sequence and the second sequence and starts from the beginning. The second semiconductor switching element Q1 can be operated normally.

Note that if the constant setting of the PFC control unit 26 is changed to reduce the responsiveness, ringing of the DC input voltage VDC can be suppressed. In this embodiment, the VDC detection is performed by the third operation start signal S3. The operation of the unit 27 is started. However, the fourth operation start signal is output from the sequence circuit unit 25 after the ringing of the DC input voltage VDC has settled to some extent, that is, when the fourth operation start time (for example, 1.0 second) has elapsed since the power was turned on. The operation of the VDC detection unit 27 may be started.
(2) Operation when an instantaneous voltage drop occurs As shown in FIG. 7, it is assumed that an instantaneous voltage drop has occurred in the AC power supply 4 at time t = t4. When an instantaneous voltage drop occurs, the DC input voltage VDC input from the DC power supply unit 3 to the step-down chopper unit 1 also decreases. When the DC input voltage VDC falls below the threshold value of the VDC detection unit 27 (time t = t5), a voltage drop signal is output from the VDC detection unit 27 to the sequence circuit unit 25.

  Upon receiving the voltage drop signal from the VDC detection unit 27, the sequence circuit unit 25 causes the first operation start signal S1, the second operation start signal S2, and the third operation start signal S3 to fall to a low level. In addition, the sequence circuit unit 25 resets the count of the cycle To and restarts the count of the cycle To from the time when the voltage drop signal is received.

  When the first operation start signal S1 falls to a low level, the PFC control unit 26 stops the first sequence and turns off the first semiconductor switching element. Similarly, when the second operation start signal S2 falls to the low level, the step-down control unit 21 stops the second sequence and turns off the second semiconductor switching element Q1. As a result, the DC power supply unit 3 and the step-down chopper unit 1 both stop operating, and the LED load 5 is turned off.

  Then, the sequence circuit unit 25 raises the first operation start signal S1 to the high level when the first operation start time has elapsed from the time when the voltage drop signal is received (time t = t6). When the first operation start signal S1 rises to the high level, the PFC control unit 26 starts the first sequence from the beginning.

  Further, the sequence circuit unit 25 raises the second operation start signal S2 to a high level when the second operation start time has elapsed from the time when the voltage drop signal is received (time t = t7). The step-down control unit 21 starts the second sequence from the beginning when the second operation start signal S2 rises to a high level. As a result, both the DC power supply unit 3 and the step-down chopper unit 1 resume operation, and the LED load 5 is lit.

  As described above, by changing the operation timing of the PFC unit 32 and the step-down chopper unit 1, it is avoided that the output voltage Vo becomes higher than the DC input voltage VDC at the timing when the step-down chopper unit 1 starts to operate. The

  Therefore, also in the LED lighting device of the present embodiment, it is avoided that the drive signal of the high side driver unit 22 is fixed to a high level, so that the capacitor C3 of the bootstrap circuit is normally charged and the terminal of the HVcc terminal A decrease in voltage can be suppressed. As a result, the LED load 5 can be prevented from remaining unlit after the instantaneous voltage drop.

1 Step-down chopper part 2 Control block 3 DC power supply part 5 LED load
21 Step-down control unit (second control unit)
25 Sequence circuit section
26 PFC controller (first controller)
27 DC voltage detector (voltage detector)
Q1 Second semiconductor switching element
T1 inductor

Claims (5)

A DC power supply unit that boosts an input voltage to a desired DC voltage; a step-down chopper unit that steps down a DC input voltage supplied from the DC power supply unit and applies it to an LED load; and the DC power supply unit and the step-down chopper unit A control block for controlling the operation,
The DC power supply unit has a boost chopper circuit having a first semiconductor switching element,
The step-down chopper section applies a second semiconductor switching element that interrupts the DC input voltage, and the DC input voltage applies energy accumulated when the DC input voltage is applied via the second semiconductor switching element. And the second semiconductor switching element is connected to a higher potential side than the inductor with respect to the DC input voltage.
The control block includes: a first control unit that performs switching control of the first semiconductor switching element according to a predetermined first sequence; a second control unit that performs switching control of the second semiconductor switching element according to a predetermined second sequence; A sequence circuit unit configured to cause the first control unit to start the first sequence and to cause the second control unit to start the second sequence; and to measure a predetermined threshold value by measuring the DC input voltage And a voltage detector that outputs a voltage drop signal when the measured value falls below the threshold value,
The sequence circuit unit is configured to cause the first control unit and the second control unit to start the first sequence and the second sequence from the beginning when receiving the voltage drop signal from the voltage detection unit. The LED lighting device characterized by the above-mentioned.   2. The LED lighting device according to claim 1, wherein the threshold value of the voltage detection unit is set to a value that is 80% of a steady-state voltage value of the DC input voltage.   3. The LED lighting device according to claim 1, wherein a voltage value in a steady state of the DC input voltage is lower than twice a rated voltage of the LED load.   The first sequence is a series of operations for the control block to feedback-control the on-duty ratio of the first semiconductor switching element of the boost chopper circuit so that the DC input voltage becomes a predetermined constant voltage. The LED lighting device according to any one of claims 1 to 3, wherein the LED lighting device is provided.   The second sequence is a series of operations for controlling the switching of the second semiconductor switching element in a discontinuous mode in which an inductor current flowing through the inductor becomes discontinuous according to a dimming signal input from the outside. The LED lighting device according to any one of claims 1 to 4, wherein the LED lighting device is provided.

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