JP2010262772A - Lighting device and method for dimming the lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply sufficient power supply voltage to an illumination circuit, even when a dimming level is changed, and to simply configure a dimming signal detection circuit. <P>SOLUTION: In a pulse modulation circuit 1, a modulation signal S11, which is obtained by superimposing dimming pulses, having a constant pulse width at pulse intervals sufficiently longer than the pulse widths of the dimming pulses, is generated on a voltage signal from a DC power supply PS. Moreover, the pulse modulation circuit 1 sets a dimming voltage which is a low level for the dimming pulse, based on the dimming voltage of a level adjustment signal Sadj. The dimming signal detection circuit 21 extracts the dimming pulse from the voltage signal to generate the dimming signal S21 of the dimming voltage Vc and supplies the generated dimming signal to the illumination circuit 23. Since the dimming voltage which is the low level of the dimming pulse is changed, when the dimming level is changed, the dimming signal detection circuit 21 can be configured simply. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lighting device and a light control method for the lighting device.

  Some lighting devices that light a discharge tube allow dimming of the discharge tube. This discharge tube is attached to a lighting fixture including a lighting circuit. A power supply line, a GND line, and a signal line for dimming signal are wired between the power supply of the lighting device and the lighting fixture.

  In recent years, a thin luminaire part has been developed, and in order to realize a thin luminaire part, it is necessary to reduce the number of wires and the number of pins of the connector of the luminaire part. Therefore, a method of omitting the signal line for the dimming signal by superimposing the dimming signal on the power supply line has been conventionally proposed.

  For example, after converting a PWM (Pulse Width Modulation) dimming signal with a pulse width set based on the dimming level into an AC signal, it is superimposed on the voltage signal from the power supply and transmitted, and the AC signal is transmitted on the lighting fixture side. There is an illuminating device in which the number of wirings is reduced by taking out the dimming signal by separating the signal and demodulating it into a PWM dimming signal (for example, see Patent Document 1).

  As another related technology, a binary code pulse train generated based on the dimming level is superimposed on the power supply line and sent to the power supply line, and the pulse signal is separated on the luminaire side and converted into a binary code by the microcomputer. There is an illuminating device in which the number of wirings is reduced so as to generate a dimming signal based thereon (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 08-102369 (page 3, FIG. 1) JP 2004-303445 A

  However, in such a lighting device, a circuit for generating a PWM dimming signal after separating an AC signal into a lighting fixture and a circuit for converting a binary coded pulse into a dimming signal by a microcomputer is required. As a result, there is a problem that the circuit becomes complicated and cannot be reduced in size and price.

  The present invention has been made in view of such conventional problems, and an illumination device capable of taking out a dimming signal superimposed on a power supply line and controlling dimming by providing a simple circuit in the lighting fixture unit. And it aims at providing the light control method of an illuminating device.

In order to achieve this object, a lighting device according to the first aspect of the present invention provides:
A light source;
A modulation signal generation unit that generates a modulation signal by superimposing a dimming pulse having a specified dimming voltage and a constant pulse width on a voltage signal supplied from a power supply at a pulse interval sufficiently longer than the pulse width of the dimming pulse. When,
A dimming signal generation unit that generates a dimming signal having a signal level corresponding to the dimming voltage of the dimming pulse superimposed on the voltage signal by the modulation signal generation unit;
A smoothing unit for smoothing the voltage signal;
An illuminating unit that sets a dimming level of the light source based on a signal level of the dimming signal generated by the dimming signal generation unit and turns on the light source with the voltage signal smoothed by the smoothing unit. It is characterized by that.

The light control method of the illumination device according to the second aspect of the present invention includes:
A dimming method for an illumination device including a light source,
Generating a modulated signal by superimposing a dimming pulse having a specified dimming voltage and a constant pulse width on a voltage signal supplied from a power supply at a pulse interval sufficiently longer than the pulse width of the dimming pulse;
Generating a dimming signal having a signal level corresponding to the dimming voltage of the dimming pulse superimposed on the voltage signal;
Smoothing the voltage signal;
Setting the dimming level of the light source based on the signal level of the generated dimming signal, and lighting the light source with the smoothed voltage signal.

  ADVANTAGE OF THE INVENTION According to this invention, the light control signal superimposed on the power wire can be taken out by providing a simple circuit in a lighting fixture part.

It is a block diagram which shows the structure of the illuminating device which concerns on embodiment of this invention. FIG. 2 is a circuit diagram showing a configuration of a pulse modulation circuit shown in FIG. 1. It is a circuit diagram which shows the structure of the illumination circuit shown in FIG. FIG. 3 is a waveform diagram of each part of the pulse modulation circuit shown in FIG. 2. It is a wave form diagram which shows operation | movement of an illuminating device, (a) shows the waveform of the modulation signal of a pulse modulation circuit, (b) shows the waveform of a modulation signal, a voltage signal, and a light control voltage. It is a wave form diagram of each part of an illuminating device. It is a circuit diagram which shows the application example of an illuminating device. FIG. 8 is a waveform diagram showing an operation of the dimming signal detection circuit shown in FIG. 7.

Hereinafter, an illumination device according to an embodiment of the present invention will be described with reference to the drawings.
The structure of the illuminating device which concerns on this embodiment is shown in FIG.
The lighting device 100 according to the present embodiment includes a pulse modulation circuit 1, a lighting fixture unit 2, a lamp 3, and a variable resistor VR.

  The variable resistor VR is a variable resistor for adjusting the dimming level of the lamp 3. One end of the variable resistor VR is connected to the pulse modulation circuit 1, and the other end is grounded, and the level adjusting signal Sadj of the dimming voltage Vs is received. This is supplied to the pulse modulation circuit 1.

  The pulse modulation circuit 1 superimposes a dimming pulse having a constant pulse width having a low level equal to the specified dimming voltage Vs on the voltage signal of the DC power supply PS at a pulse interval sufficiently longer than the pulse width of the dimming pulse. The modulation signal S11 is generated, and includes a pulse oscillator 11, a delay unit 12, a modulation unit 13, and a dimming voltage setting unit 14, as shown in FIG.

  The pulse oscillator 11 generates a pulse signal S0 having a constant pulse width period T11 and a pulse interval T0 as shown in FIG. Here, the pulse interval T0 is set sufficiently larger than the pulse width period T11.

  The delay unit 12 generates, from the pulse signal S0 output from the pulse oscillator 11, two pulse signals S1 and S2 having falling and rising timings as drive signals so that the transistors Q11 and Q12 are not simultaneously turned on. It is.

  The delay unit 12 includes resistors R1 and R2, capacitors C1 and C2, and diodes D1 and D2.

  One end of the resistor R1 is connected to the output end of the pulse oscillator 11, one end of the capacitor C1 is connected to the other end of the resistor R1, and the other end of the capacitor C1 is grounded.

  The cathode of the diode D1 is connected to the output end of the pulse oscillator 11 and one end of the resistor R1, and the anode is connected to the other end of the resistor R1 and one end of the capacitor C1. The delay unit 12 supplies a signal at a connection point between the resistor R1 and the capacitor C1 to the modulation unit 13 as a pulse signal S1.

  One end of the resistor R2 is connected to the output end of the pulse oscillator 11, one end of the capacitor C2 is connected to the other end of the resistor R2, and the other end of the capacitor C2 is grounded.

  The anode of the diode D2 is connected to the output terminal of the pulse oscillator 11, and the cathode is connected to the connection point between the resistor R2 and the capacitor C2. The delay unit 12 supplies a signal at a connection point between the resistor R2 and the capacitor C2 to the modulation unit 13 as a pulse signal S2.

  The modulation unit 13 is supplied with the voltage signal of the voltage Vcc from the DC power supply PS, and switches the voltage signal of the voltage Vcc based on the pulse signal S0 generated by the pulse oscillator 11, thereby applying the dimming pulse P1 to the voltage signal. The gate drivers DR1 and DR2 and transistors Q11 and Q12 are included.

  The gate drivers DR1 and DR2 turn on and off the transistors Q11 and Q12, respectively, and pulse signals S1 and S2 generated based on the pulse signal S0 are supplied from the delay unit 12, and the pulse signals S1 and S2 Are inverted and amplified to generate gate signals S3 and S4, which are applied to the gates of the transistors Q11 and Q12.

  The transistors Q11 and Q12 are turned on and off based on the pulse signals S1 and S2 supplied from the gate drivers DR1 and DR2, respectively, and output a modulation signal S11.

  The transistor Q11 is a p-channel MOSFET (Metal-Oxide Semiconductor Field Effect Transistor), and its source is connected to the positive electrode of the DC power source PS of the DC voltage Vcc, and a voltage signal of the DC voltage Vcc is supplied. The transistor Q11 is turned off when a gate signal S3 of High level is supplied to the gate, and is turned on when the gate signal S3 becomes Low level.

  The transistor Q12 is an n-channel MOSFET, and the drain is connected to the drain of the transistor Q11. A connection point between the transistor Q11 and the transistor Q12 is a node N11, and the node N11 is connected to the output terminal of the pulse modulation circuit 1. The transistor Q12 is turned on when a gate signal S4 of High level is supplied to the gate, and is turned off when the gate signal S4 becomes Low level.

  The dimming voltage setting unit 14 sets the dimming voltage Vs (source voltage of the transistor Q12) of the dimming pulse P1 based on the supplied level adjustment signal Sadj, and includes an operational amplifier IC1 and a capacitor C3. .

  The operational amplifier IC1 is an operational amplifier for supplying the supplied level adjustment signal Sadj to the capacitor C3. The inverting input terminal (−) of the operational amplifier IC1 is connected to one end of the variable resistor VR, and the output terminal is connected to the non-inverting input terminal (+) and one end of the capacitor C3 to constitute a voltage follower circuit.

  The capacitor C3 is for determining the source voltage of the transistor Q12 based on the signal level of the level adjustment signal Sadj, one end of which is connected to the output end of the operational amplifier IC1 and the source of the transistor Q12, and the other end. Is grounded.

  While the transistor Q12 is on, the voltage signal supplied from the DC power source PS decreases. The signal in which the voltage signal decreases is the dimming pulse P1, and the dimming pulse P1 is superimposed on the voltage signal. The source voltage of the transistor Q12 becomes the dimming voltage Vs of the dimming pulse P1 superimposed on the modulation signal S11.

  The pulse interval T0 of the dimming pulse P1 is determined by the pulse signal S0 output from the pulse oscillator 11. Further, even if the dimming voltage Vs of the level adjustment signal Sadj input to the dimming voltage setting unit 14 changes, the pulse width period T1 in which the dimming pulse P1 is at the low level does not change, and the dimming pulse P1 The Low level becomes the dimming voltage Vs of the level adjustment signal Sadj.

  The pulse modulation circuit 1 increases its duty sufficiently so that the dimming signal does not affect the voltage supply to the luminaire unit 2.

  Specifically, the pulse modulation circuit 1 superimposes a pulse-shaped dimming pulse P1 having a pulse width period T1 of about 0.1 to 1 ms and a pulse interval period T2 of about 10 to 200 ms on the voltage signal.

  Returning to FIG. 1, the luminaire unit 2 lights the lamp 3 and performs dimming of the lamp 3 according to the dimming voltage Vs. The dimming signal detection circuit 21, the smoothing circuit 22, the lighting circuit 23, . The lighting fixture 2 includes a dimming (power supply) input terminal and a GND terminal, and the dimming (power supply) input terminal is connected to the output terminal of the pulse modulation circuit 1.

  The dimming signal detection circuit 21 extracts the dimming pulse P1 from the modulation signal S11 supplied from the pulse modulation circuit 1 via the dimming input terminal, and converts it into a DC dimming voltage as a signal level corresponding to the dimming voltage Vs. This circuit generates a Vc dimming signal S21, and includes a resistor R21, a capacitor C21, and a diode D21.

  The resistor R21 is a current limiting resistor that limits the current flowing into the capacitor C21. One end of the resistor R21 is connected to the node N11 illustrated in FIG. 2 via the output end of the pulse modulation circuit 1. One end of the capacitor C21 is connected to the other end of the resistor R21, and the other end of the capacitor C21 is grounded.

  The diode D21 is a discharge diode that discharges the electric charge of the capacitor C21, and is formed of a silicon semiconductor. The cathode of the diode D21 is connected to one end of the resistor R21, and the anode is connected to the other end of the resistor R21 and one end of the capacitor C21.

  The signal level Vc of the dimming signal S21 generated by the dimming signal detection circuit 21 is determined by the low level of the dimming pulse P1, that is, the dimming voltage Vs.

  The smoothing circuit 22 is a circuit that generates the voltage signal S22 of the DC voltage Va by removing the dimming pulse P1 from the modulation signal S11 and smoothing the voltage signal, and includes a diode D22 and a capacitor C22.

  The diode D22 is a smoothing diode, and its anode is connected to the node N11 via the output terminal of the pulse modulation circuit 1, and its cathode is connected to the power supply input terminal of the illumination circuit 23.

  The capacitor C22 is a smoothing capacitor, one end of which is connected to the cathode of the diode D22 and the other end is grounded.

  The illumination circuit 23 is a circuit for lighting the lamp 3, and includes a transformer T, transistors Q31 and Q32, a driver 31, and a capacitor C31 as shown in FIG. 3, and is configured by a push-pull circuit. The

  The transformer T includes a primary winding and a secondary winding, and a DC voltage Va is applied to the primary winding to transmit energy accumulated in the primary winding to the secondary winding. . The midpoint of the primary winding is connected to the cathode of the diode D22 of the smoothing circuit 22 and one end of the capacitor C22. Both ends of the secondary winding are connected to both ends of the lamp 3, respectively.

  The transistors Q31 and Q32 are switching transistors for alternately turning on and off to accumulate energy in the primary winding of the transformer T, and n-channel MOSFETs are used.

  The transistors Q31 and Q32 are turned on when the gates S31 and S32 of High level are supplied to the gates, respectively.

  The drain of the transistor Q31 is connected to one end of the transformer T, and the source is grounded. The drain of the transistor Q32 is connected to the other end of the transformer T, and the source is grounded.

  The driver 31 alternately supplies high-level gate signals S31 and S32 to the gates of the transistors Q31 and Q32 to drive the transistors Q31 and Q32.

  The driver 31 sets the on-duty of the gate signals S31 and S32 supplied to the gates of the transistors Q31 and Q32 according to the dimming voltage Vc of the dimming signal S21 supplied from the dimming signal detection circuit 21.

  A period in which the gate signal S31 and the gate signal S32 are at a high level is an on period Ton of the transistors Q31 and Q32, and the on duty is a ratio of the on period Ton to the switching period Tsw.

  The driver 31 performs PWM control on the transistors Q31 and Q32 by alternately supplying the gate signals S31 and S32 with the on-duty set to the gates of the transistors Q31 and Q32.

  Further, as another dimming means, the driver 31 provides a pause period of a fixed period for the gate signals S31 and S32 supplied to the respective gates of Q31 and Q32, and the dimming signal S21 supplied from the dimming signal detection circuit 21 is provided. In accordance with the dimming voltage Vc, the length of the pause period can be varied to change the ratio of the lighting and non-lighting periods of the lamp 3 so as to realize dimming.

  The lamp 3 is a light source such as a cold cathode fluorescent lamp or a hot cathode fluorescent lamp, for example, and is an illumination member that utilizes two phenomena of “discharge” and “fluorescence”. Both ends of the lamp 3 are connected to output terminals Pout1 and Pout2 of the illumination circuit 23, respectively.

Next, operation | movement of the illuminating device 100 which concerns on this embodiment is demonstrated.
In the pulse modulation circuit 1, the pulse oscillator 11 generates a pulse signal S 0 and supplies it to the delay unit 12.

  As shown in FIG. 4, when the pulse signal S0 generated by the pulse oscillator 11 falls at time t11, the capacitor C1 is discharged via the diode D1. For this reason, the pulse signal S1 falls almost simultaneously with the fall of the pulse signal S0.

  On the other hand, since the capacitor C2 is discharged through the resistor R2, the pulse signal S2 falls with a delay of time Td1 from the fall of the pulse signal S0.

  When the pulse signal S0 rises at time t12, the capacitor C1 is charged via the resistor R1. Therefore, the pulse signal S1 rises with a delay of time Td2 from the rise of the pulse signal S0.

  On the other hand, since the capacitor C2 is charged via the diode D2, the pulse signal S2 rises almost simultaneously with the rise of the pulse signal S0.

  In this way, the rising timing and falling timing of the pulse signals S1, S2 are shifted. The delay unit 12 supplies the pulse signals S1 and S2 to the drivers DR1 and DR2 of the modulation unit 13, respectively.

  The drivers DR1 and DR2 invert and amplify the pulse signals S1 and S2 supplied from the delay unit 12 and apply them to the gates of the transistors Q11 and Q12, respectively.

  The transistor Q11 is turned off almost simultaneously with the time t11 and turned on with a delay of time Td2 from the time t12. The transistor Q12 is turned on with a delay of time Td1 from the time t11, and is turned on at substantially the same time as the time t12.

  For this reason, as shown in FIG. 4, the transistors Q11 and Q12 are not turned on at the same time, and the modulation signal S11 in which the dimming pulse P1 is superimposed on the voltage signal of the voltage Vcc is generated.

  The modulation signal S11 is transmitted to the lighting fixture 2 and supplied to the dimming signal detection circuit 21. The dimming signal detection circuit 21 detects and extracts the dimming signal S21 from the modulation signal S11.

  As shown in FIG. 5A, when the dimming voltage Vs is set to the voltage Vs1 at time t21, the dimming voltage Vs of the modulation signal S11 decreases to the voltage Vs1.

  As shown in FIG. 5B, the charge of the capacitor C21 is rapidly discharged through the diode D21 to the voltage Vc11 simultaneously with the fall of the dimming pulse P1 from the time t21. Here, Vc11 is lower than the voltage Vs1 by the forward voltage drop of the diode D21.

  When the period of the pulse width period T1 elapses and the voltage level of the modulation signal S11 rises to the voltage Vcc, the capacitor C21 is charged via the resistor R21.

  The dimming voltage Vc of the dimming signal S21 rises as shown in FIG. 5B, and reaches the voltage Vc12 within the pulse interval period T2. Each time the dimming pulse P1 enters, charging and discharging of the capacitor C21 is repeated as described above, and the voltage of the capacitor C21 becomes a DC voltage including a sawtooth wave component. The dimming signal detection circuit 21 supplies the dimming signal S21, which is the voltage of the capacitor C21, to the illumination circuit 23.

  Here, in order for the illuminating device 23 to operate stably, it is desirable that the sawtooth wave component is small. This sawtooth wave component can be reduced as the interval of the dimming pulse P1 is shorter, or as the values of the resistor R21 and the capacitor C21 are larger. However, when the interval of the dimming pulse P1 is extremely reduced, There is an adverse effect that the applied voltage signal S22 is lowered.

  Further, if the values of the resistor R21 and the capacitor C21 are extremely increased, an adverse effect that the response time for the dimming to follow with respect to the change of the dimming signal Sadj occurs. Therefore, the constant is determined in consideration of these.

  On the other hand, the smoothing circuit 22 removes the dimming pulse P1 from the modulation signal S11 and generates a voltage signal S22 of the DC voltage Va. As shown in FIG. 5B, the voltage Va of the voltage signal S22 after the dimming pulse P1 is removed decreases from the voltage Vcc of the modulation signal S11 by the forward voltage drop VF of the diode D21. The smoothing circuit 22 supplies the voltage signal S22 of the voltage Va to the lighting circuit 23.

  During the period (T1) during which the dimming pulse P1 is output, the voltage of the modulation signal S11 is lower than the voltage signal S22, which is the charging voltage of the capacitor C22, and the diode D22 is biased in the reverse direction, so that no current flows. The signal S22 decreases.

  However, since the decrease in the voltage signal S22 is compensated for by the discharge current of the capacitor C22 during the period (T1) during which this P1 is output, the capacity of the capacitor C22 is increased or the dimming pulse width T1 is sufficiently shortened. Thus, the decrease of the voltage signal S22 can be reduced, and the influence of the voltage signal S22 on the voltage Va can be reduced.

  This voltage Va is applied to the middle point of the primary winding of the transformer T of the illumination circuit 23. The illumination circuit 23 sets on-duties of the gate signals S31 and S32 based on the voltage Vc12 shown in FIG. 5B, and supplies the gate signals S31 and S32 to the gates of the transistors Q31 and Q32.

  The transistors Q31 and Q32 are turned on when the gate signals S31 and S32 of High level are supplied to the gates, respectively, and are turned off when the gate signals S31 and S32 become Low level. The drain-source voltages Vds1 and Vds2 of the transistors Q31 and Q32 at this time have waveforms as shown in FIG.

  The transistors Q31 and Q32 are alternately turned on to accumulate energy in the primary winding, and when each is turned off, energy is transmitted to the secondary winding. In the secondary winding, an AC voltage is generated by multiplying the turn ratio of the primary winding and the secondary winding by the on-duty.

  This voltage is applied to both ends of the lamp 3, and the lamp 3 is lit by being supplied with a resonated current by the secondary winding and the capacitor C31.

  As shown in FIG. 5A, when the dimming voltage Vs of the level adjustment signal Sadj is set to the voltage Vs2 at time t22 (Vs1> Vs2), as shown in FIG. The dimming voltage Vc of S21 decreases to Vc21 (Vc11> Vc21).

  When the pulse width period T1 elapses and the voltage of the modulation signal S11 rises to the voltage Vcc, the dimming voltage Vc of the dimming signal S21 rises to the voltage Vc22 as shown in FIG. 5B. Since Vc11> Vc21, the voltage Vc22 is also lower than the voltage Vc12.

  On the other hand, even if the dimming voltage Vs changes from the voltage Vs1 to the voltage Vs2, the pulse width period T1 of the modulation signal S11 is constant. Therefore, the voltage Va of the voltage signal S22 is equal to the forward voltage drop VF of the diode D22. , It will only drop, but not below that.

  Since the voltage Vc22 of the dimming signal S21 is lower than the voltage Vc12, the on-duty set by the driver 31 becomes small, and the on-period Ton of the transistors Q31 and Q32 becomes short as shown in FIG. 6 (Ton1> Ton3 , Ton2> Ton4).

  For this reason, the voltage generated in the secondary winding of the transformer T decreases, the current supplied to the lamp 3 also decreases, and the dimming level decreases.

  As described above, according to the present embodiment, the illumination device 100 changes the low level of the dimming pulse P1 when the dimming voltage Vs of the level adjustment signal Sadj input to the pulse modulation circuit 1 changes. I did it.

  In addition, since the dimming signal detection circuit 21 is configured to extract information on the dimming voltage Vs from the low level of the dimming pulse P1, the configuration of the dimming signal detection circuit 21 is simple and low in cost. It can also be suppressed.

  Further, since the dimming pulse P1 is superimposed on the voltage signal from the DC power supply PS, there is no need to lay a dedicated dimming signal cable, and the dimming input terminal can be reduced, and the luminaire unit 2 can be made thinner. .

  In carrying out the present invention, various forms are conceivable and the present invention is not limited to the above embodiment.

  For example, in the above-described embodiment, the lighting device 100 may include the dimming signal detection circuit 24 configured as shown in FIG. 7 instead of the dimming signal detection circuit 21 as shown in FIG.

  In the dimming signal detection circuit 21 shown in FIG. 1, the dimming voltage Vc includes a sawtooth wave component although it is almost direct current as shown in FIG. 5B.

  The dimming signal detection circuit 24 configured as shown in FIG. 7 is configured to remove this sawtooth wave component.

  The dimming signal detection circuit 24 includes a transistor Q24, resistors R24 and R25, and a capacitor C24 in addition to the configuration of the dimming signal detection circuit 21 shown in FIG.

  The transistor Q24 is an npn-type bipolar transistor and is formed of the same silicon semiconductor as the diode D21. The collector of the transistor Q24 is connected to the cathode of the diode D22 of the smoothing circuit 22 and one end of the capacitor C22, and the base is connected to the connection point between the anode of the diode D21, the other end of the resistor R21, and one end of the capacitor C21. .

  The resistors R24 and R25 are voltage dividing resistors. One end of the resistor R24 is connected to the emitter of the transistor Q24, one end of the resistor R25 is connected to the other end of the resistor R24, and the other end of the resistor R25 is grounded. One end of the capacitor C24 is connected to a connection point between the resistor R24 and the resistor R25, and the other end is grounded.

  The transistor Q24 operates according to the dimming voltage Vc of the dimming signal S21 supplied to the base. The sawtooth ripple component is removed by a circuit composed of voltage dividing resistors R24 and R25 and a capacitor C21.

  Next, the relationship between the forward voltage drop VF of the diode D21 and the forward voltage VF ′ of the diode component of the transistor Q24 will be described.

  The dimming voltage Vc at the connection point between the resistor R21 and the capacitor C21 is a voltage obtained by adding the forward voltage drop VF of the diode D21 as an error. On the other hand, since a diode component exists between the base and emitter of the transistor Q24, a voltage obtained by subtracting the dimming voltage Vc from the forward voltage VF 'of the diode component is generated at the emitter of the transistor Q24.

  Here, in the case of a junction type diode or transistor, the forward voltage VF of the diode and the forward voltage VF ′ of the diode component of the transistor are substantially equal.

  Accordingly, the forward voltage VF of the diode D21 which is a junction type diode and the forward voltage VF ′ of the diode component of the transistor Q24 are substantially equal, and the voltage generated at the emitter of the transistor Q24 is substantially equal to the dimming voltage Vs. Will be equal.

  Further explaining the temperature change, the forward voltage drop VF of the diode D21 depends on the temperature. In the case of a silicon diode, the temperature coefficient of the forward voltage VF is about −2 mV / ° C., and when the temperature changes, the forward voltage drop VF of the diode D21 also changes.

  However, the junction-type diode and the transistor have substantially the same temperature characteristics. If the temperature changes, the forward voltage drop VF ′ of the diode component of the transistor Q24 changes in the same way.

  Therefore, even if the temperature changes, the forward voltage drop VF ′ and the forward voltage drop VF cancel each other, and a voltage that is hardly affected by the temperature change appears at the emitter of the transistor Q24.

  The voltage dividing resistors R24 and R25 divide the voltage appearing at the emitter of the transistor Q24, and, as shown in FIG. 8, the dimming signal S24 of the dimming voltage Vc ′ from which the sawtooth ripple component is removed is shown in the illumination circuit. 23.

  With such a configuration of the dimming signal detection circuit 24, a DC dimming signal S24 with a small ripple component can be supplied to the illumination circuit 23, the light quantity of the lamp 3 is more stable, and flickering occurs. It can be surely prevented.

  In order to make the temperature change received by the diode D21 and the temperature change received by the transistor Q24 the same, it is desirable that the diode D21 and the transistor Q24 be arranged as close as possible.

  In this way, the temperature conditions are the same, and more accurately, the fluctuation due to the temperature change of the forward voltage drop VF of the diode D21 and the fluctuation due to the temperature change of the base-emitter forward voltage drop VF of the transistor Q24. Can cancel each other, and the influence of the temperature of the source voltage and dimming voltage Vc ′ generated in the transistor Q24 can be reduced.

  Next, in the above embodiment, the light source has been described as the lamp 3 such as a cold cathode fluorescent lamp or a hot cathode fluorescent lamp. However, the light source is not limited to such a lamp 3 and may be, for example, a light emitting diode or an organic EL.

  Further, the illumination circuit 23 is not limited to the push-pull circuit as shown in FIG. 3, and may be a half bridge circuit or a full bridge circuit. If the light source is other than a cold cathode fluorescent lamp or a hot cathode fluorescent lamp, the illumination circuit 23 has a configuration corresponding to the light source.

DESCRIPTION OF SYMBOLS 1 Pulse modulation circuit 2 Lighting fixture part 3 Lamp 11 Pulse oscillator 12 Delay part 13 Modulation part 14 Dimming voltage setting part 21, 24 Dimming signal detection circuit 22 Smoothing circuit 23 Lighting circuit 100 Illuminating device

Claims (7)

A light source;
A modulation signal generation unit that generates a modulation signal by superimposing a dimming pulse having a specified dimming voltage and a constant pulse width on a voltage signal supplied from a power supply at a pulse interval sufficiently longer than the pulse width of the dimming pulse. When,
A dimming signal generation unit that generates a dimming signal having a signal level corresponding to the dimming voltage of the dimming pulse superimposed on the voltage signal by the modulation signal generation unit;
A smoothing unit for smoothing the voltage signal;
An illuminating unit that sets a dimming level of the light source based on a signal level of the dimming signal generated by the dimming signal generation unit and turns on the light source with the voltage signal smoothed by the smoothing unit. The
A lighting device characterized by that. The dimming signal generation unit extracts the dimming pulse superimposed on the voltage signal by the modulation signal generation unit from the voltage signal, and smoothes the extracted dimming pulse to correspond to the dimming voltage. Generate a signal level dimming signal,
The lighting device according to claim 1. The dimming signal generator is
A current limiting resistor having one end connected to the output end of the modulation signal generator;
A first capacitor having one end connected to the other end of the current limiting resistor and the other end grounded;
A discharge diode for discharging a charge of the first capacitor by connecting a cathode to one end of the current limiting resistor and an anode connected to the other end of the current limiting resistor and one end of the first capacitor; ,
A signal smoothed by the first capacitor is supplied to the illumination unit as a first dimming signal;
The illumination device according to claim 1, wherein The smoothing part is
A rectifier diode having an anode connected to the output end of the modulation signal generation unit and a cathode connected to the input end of the illumination unit;
A smoothing capacitor having one end connected to the cathode of the rectifier diode and the other end grounded,
The dimming signal generator is
A collector is connected to the cathode of the rectifier diode of the smoothing unit and one end of the smoothing capacitor, and a base is the anode of the first diode, the other end of the current limiting resistor, and one end of the first capacitor. A bipolar transistor to which the first dimming signal is supplied connected to the connection point of
A voltage dividing resistor connected in series to the emitter of the bipolar transistor;
A second capacitor having one end connected to the connection point of the voltage dividing resistor and the other end grounded,
A signal at a connection point between the voltage dividing resistor and one end of the second capacitor is supplied to the illumination unit as a second dimming signal.
The lighting device according to claim 3. The modulation signal generator is
A pulse oscillator for generating a pulse signal having a pulse interval sufficiently longer than a pulse width of the dimming pulse, the dimming pulse having a constant pulse width;
A modulation unit that superimposes the dimming pulse on the voltage signal by switching the supplied voltage signal based on the pulse signal generated by the pulse oscillator, the voltage signal being supplied from the power source;
A dimming voltage setting unit for setting a dimming voltage of the dimming pulse to be superimposed by the modulation unit,
The lighting device according to any one of claims 1 to 4, wherein The modulation signal generator is
From the pulse signal generated by the pulse oscillator, a drive signal generation unit that generates two drive signals with the falling and rising timings shifted, and supplies the generated two drive signals to the modulation unit,
The modulation unit switches the voltage signal based on the two drive signals generated by the drive signal generation unit,
The lighting device according to claim 5. A dimming method for an illumination device including a light source,
Generating a modulated signal by superimposing a dimming pulse having a specified dimming voltage and a constant pulse width on a voltage signal supplied from a power supply at a pulse interval sufficiently longer than the pulse width of the dimming pulse;
Generating a dimming signal having a signal level corresponding to the dimming voltage of the dimming pulse superimposed on the voltage signal;
Smoothing the voltage signal;
Setting the dimming level of the light source based on the signal level of the generated dimming signal, and lighting the light source with the smoothed voltage signal,
A lighting control method for an illuminating device.

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