JP2012174536A - Power circuit for lighting and lighting device - Google Patents

Abstract

Provided is a lighting power supply circuit that suppresses an increase in special manufacturing management processes and mounting parts, and has little variation (fluctuation) in illuminance due to an individual.
An illumination power supply circuit that supplies a DC current generated by rectifying and smoothing an AC voltage to a lighting lamp so that the average of the current supplied to the lighting lamp is constant. An adjustment circuit Oj that adjusts the current value detection level of the detection current according to the fluctuation of the oscillation frequency of the oscillator 63 is provided.
[Selection] Figure 1

Description

  The present invention relates to an illumination power supply circuit used for LED illumination or the like and an illumination device using the same.

  As a conventional illumination power supply device, for example, there is one disclosed in Japanese Patent Application Laid-Open No. 2008-52994. FIG. 8 is a diagram showing a conventional illumination power supply device. The lighting power supply device shown in FIG. 8 converts the current supplied to the LED (LED supply current) into a voltage by a resistor R5, and the amplifier 16 uses the peak value of the voltage (peak voltage) and a reference. The difference from the voltage is amplified. Then, the comparator 18 compares the output of the amplifier 16 with the oscillation signal from the oscillator 17, and a square wave signal whose logic level is high during a period when the voltage of the output signal of the amplifier 16 is smaller than the signal voltage of the oscillator 17. Is output.

  The output signal from the comparator 18 is input to the transistor Q1. The transistor Q1 is turned on by an output signal from the comparator 18, and when the transistor Q1 is turned on, the transistor Q2 is also turned on.

  The specific operation of the conventional illumination power supply device is as follows. When the peak voltage is higher than the reference voltage in the amplifier 16, the on period of the transistor Q1 due to the output signal from the comparator 18 is shortened, and the on period of the transistor Q2 synchronized with the transistor Q1 is also shortened. At this time, since the off period of the transistor Q2 becomes longer, the peak value of the LED supply current I decreases and the peak voltage also decreases. On the other hand, when the peak voltage is smaller than the reference voltage, the ON period of the transistor Q2 becomes longer and the peak voltage becomes larger. The ON / OFF period of the output signal from the comparator 18 is adjusted based on the oscillation frequency (number of clocks) set by the oscillator 17.

  That is, when the peak voltage is larger than the predetermined voltage, the time for supplying the LED supply current is shortened, and when the peak voltage is smaller than the predetermined voltage, the time for supplying the LED supply current is lengthened. Thereby, the peak value of the LED supply current supplied to the LED is adjusted to be constant, and the brightness of the lighting device is kept constant.

  FIG. 9 shows a non-insulated illumination power supply circuit used in a general illumination device. The illumination power supply circuit E shown in FIG. 9 supplies power from the AC power supply 1 to the LED module 4 having a plurality of LEDs via the rectifier circuit 2 and the smoothing circuit 3. The other terminal of the LED module 4 is connected to the collector (drain) of the switching transistor 5 through the coil L1, and the LED supply current is supplied to the LED module 4 by controlling the switching transistor 5 by the switching transistor control circuit 96. It is the composition to do.

  As shown in FIG. 9, the rectifier circuit 2 is a diode bridge, and is a circuit that rectifies the AC supplied from the AC power supply 1. The output current of the rectifier circuit 2 has a pulse wave component. The smoothing circuit 3 smoothes the pulse wave component by using the charging / discharging action of the capacitor and the frequency characteristics of the AC resistance of the coil, and outputs a DC waveform current (DC current). Note that the rectifier circuit 2 and the smoothing circuit 3 are well-known circuits, and details thereof are omitted.

  In the illumination power supply circuit E, energy is accumulated in the coil L1 while the LED supply current flows through the LED module 4. The lighting power supply circuit E is connected to the freewheeling diode Df1 so that the energy of the coil L1 is supplied to the anode side of the LED module 4 after the power supply from the smoothing circuit 3 is stopped. Since the energy accumulated in the coil L1 is supplied to the LED module 4, a current flows through the LED module 4 for a while after the power supply is stopped.

  The emitter (source) of the switching transistor 5 is connected to the ground power supply via the current value detection resistor Rs. The current value detection resistor Rs detects the emitter (source) current of the switching transistor 5 and converts the detected current value of the detected current into a voltage. The voltage (detected) converted (detected) by the current value detection resistor Rs is linked to the LED supply current and is input to the switching transistor control circuit 96. A control signal from the switching transistor control circuit 96 is input to the base (gate) of the switching transistor 5. The switching transistor 5 is on / off controlled by this control signal. The switching transistor control circuit 96 includes a comparator 61, a power source 62, an oscillator 63, and a flip-prop 64.

  The switching transistor control circuit 96 outputs a comparison result between a detection voltage obtained by converting the detection current detected by the current value detection resistor Rs and a constant voltage (referred to as a reference voltage) output from the power source 62 and the oscillator 63. The on / off duty of the control signal is adjusted based on the oscillation frequency (number of clocks) of the oscillation signal (clock pulse) to be adjusted, and the on / off period of the switching transistor is adjusted.

  A specific operation of the switching transistor control circuit 96 will be described. FIG. 10A is a timing chart of the operation of the switching transistor drive circuit in the conventional illumination power supply circuit. In the timing chart shown in FIG. 10A, a (a1 in FIG. 10A) is a voltage waveform of a detection voltage obtained by detecting the LED supply current flowing through the LED module 4 with the current value detection resistor Rs, and b (b1 in FIG. 10A) is This is a voltage waveform of a reference voltage output from the power supply 62, and c (c1 in FIG. 10A) indicates a waveform of a control signal input to the base (gate) of the switching transistor 5. I is the current waveform of the LED supply current that actually flows through the LED module, and ILED indicates the average value (LED drive current) of the LED supply current.

  In the switching transistor control circuit 96, the comparator 61 compares the detected voltage with the reference voltage, and the result is input to the reset terminal of the flip-flop 64. An oscillation signal from the oscillator 63 is input to the set terminal of the flip-flop 64. It is assumed that the oscillation frequency (clock number) of the oscillation signal (clock pulse) output from the oscillator 63 is constant.

  When the LED supply current does not flow through the LED module 4, the detection voltage is 0 V, which is lower than the reference voltage, so that the comparator 61 outputs a low level. That is, the reset terminal of the flip-flop 64 is at a low level. The flip-flop 64 outputs a high level according to the rising timing of the oscillation signal, and turns on the switching transistor 5 (see the signal waveform c1).

  The LED supply current is supplied to the LED module 4 by turning on the switching transistor 5. The LED supply current increases after the switching transistor 5 is turned on, and accordingly, the detection voltage increases (upper right part of the voltage waveform a1). When the detection voltage increases and reaches the reference voltage (the point where the voltage waveform a1 and the voltage waveform b1 are in contact), a high level is output from the comparator 61, the output of the flip-flop 64 becomes a low level, and the switching transistor 5 Is turned off (see signal waveform c1), and the LED supply current is cut off.

  Further, the LED supply current is actually represented by a current waveform I in FIG. 10A. The waveform of the current flowing through the switching transistor 5 has a shape similar to the voltage waveform a1 of the detection voltage. That is, the current starts to flow when the switching transistor 5 is turned on, and is cut off when the switching transistor 5 is turned off so that no current flows. However, even after the switching transistor 5 is turned off, the energy stored in the coil is supplied to the LED module 4 via the free-wheeling diode Df1, and a current flows until the coil energy is exhausted. The average value ILED of the current waveform I is supplied as the average current (LED drive current) flowing through the LED module 4 to emit light.

  The detailed description will be given separately for cases where the reference voltage is high and low. FIG. 10B is a timing chart of the switching transistor drive circuit when the reference voltage is lower than that in FIG. 10A. Comparing FIG. 10A and FIG. 10B, if the reference voltage is high, it takes time until the detection voltage reaches the reference voltage. For this reason, the time during which the output from the flip-flop 64 is at a high level is lengthened, and the ON period of the switching transistor 5 is lengthened (see the signal waveform c1 in FIG. 10A). Conversely, when the reference voltage is low, the time until the detection voltage reaches the reference voltage is shortened. Therefore, the ON period of the switching transistor 5 is shortened (see the signal waveform c2 in FIG. 10B). That is, the switching transistor control circuit 96 can adjust the LED drive current ILED supplied to the LED module 4 by adjusting the reference voltage.

  Further, as described above, the switching transistor drive circuit 96 turns on the switching transistor 5 every time the oscillation signal (clock pulse) from the oscillator 63 rises. That is, in the lighting device, the LED drive current supplied to the LED module 4 varies depending on the oscillation frequency (number of clocks) of the oscillator 63. FIG. 11A to FIG. 11B show timing charts of the switching transistor drive circuit when driven by changing the oscillation frequency of the oscillator in the state of FIG. 10A. Since FIG. 11A is driven at the same oscillation frequency as FIG. 10A, details are omitted.

  As shown in FIGS. 11A to 11B, the switching transistor 5 is turned on each time the oscillation signal (clock pulse) output from the oscillator 63 rises. As shown in FIG. 11B, when the oscillation frequency (number of clocks) of the oscillator 63 increases (compared to FIG. 11A), the number of times the switching transistor 5 is turned on per unit time (the ON density of the switching transistor 5) increases. Therefore, the current supplied to the LED module also increases. Therefore, the LED drive current ILED supplied to the LED module 4 varies depending on the oscillation frequency (number of clocks) of the oscillator 63.

  As described above, in the conventional lighting device shown in FIG. 8 (Japanese Patent Laid-Open No. 2008-52994) and the non-insulated lighting device shown in FIG. Varies with the oscillation frequency.

JP 2008-52994 A

  The switching transistor drive circuit is often supplied as an integrated circuit (IC) (sometimes referred to as a switching transistor drive IC). Usually, the oscillator 63 is often built in a switching transistor driving IC and is formed on the same semiconductor substrate as other electronic components. The oscillation frequency (number of clocks) of the oscillator is designed to be set by a current value and a capacitance value, and the current value is generated using a resistor. In semiconductor processes, variations (variations) may occur in resistance values of resistors mounted on a substrate (manufacturing variations, etc.). When variations occur in the resistance value that generates the current that biases the oscillator, the oscillation frequency (number of clocks) of the oscillator also varies.

  As described above, the number (density) of ON / OFF of the switching transistor is determined by the oscillation frequency of the oscillator. When the oscillation frequency (number of clocks) of the oscillator varies, the number of ON / OFF of the switching transistor (density) is There arises a problem that the brightness and brightness (illuminance) of the lighting device vary from one individual to another (a product having brightness characteristics varies).

  If an attempt is made to manufacture a switching transistor driving IC so that variations in brightness (illuminance) as an illuminating device are within an allowable range, the accuracy required for the switching transistor driving IC becomes very high. Strict process control is required to suppress resistance variation (fluctuation) so as to satisfy the requirements in the semiconductor process. Furthermore, a product check such as a screening test within a certain range is required. The increase in process management and the selection test lowers the yield and raises the problem of increasing the manufacturing cost of the switching transistor driving IC.

  By using the oscillator as an external component, it is possible to suppress variations in the oscillation frequency (number of clocks) of the oscillator by managing the accuracy of the components used. However, as the number of crystal elements constituting the oscillator increases, the component cost increases. Further, an oscillator must be mounted in addition to the IC package, resulting in an increase in assembly and mounting costs. Furthermore, when the number of mounted parts increases, the mounting board of the lighting power supply device must be enlarged, and cannot be stored in a lighting device such as a light bulb, or there is a problem that the degree of freedom of design decreases. There is also.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a lighting power supply circuit that suppresses a special manufacturing control process and an increase in mounting parts, and has little variation (fluctuation) in illuminance due to an individual.

  In order to achieve the above object, the present invention provides a lighting power supply circuit that supplies a direct current generated by rectifying and smoothing an alternating voltage to an illumination lamp, the coil through which the direct current flows, and at least the coil. A reflux diode connected in anti-parallel, a switching element connected in series with the coil to adjust the current supplied to the illumination lamp, a detection means for detecting the current flowing through the switching element, and an internal device A control circuit for controlling on / off of the switching element based on the value of the oscillation signal of the oscillation means and the detection current detected by the detection means; and the detection current according to the fluctuation of the oscillation frequency of the oscillation signal of the oscillation means An adjustment circuit for adjusting the current value detection level is provided.

  According to this configuration, the adjustment circuit adjusts the current value detection level of the detection current according to the fluctuation of the oscillation frequency of the oscillation signal so that the average value of the current supplied to the illumination lamp is constant. Therefore, it is possible to suppress variation (variation) in the current flowing through the illumination lamp.

  Even if the oscillation means that is likely to vary in the semiconductor manufacturing process is integrated in an integrated circuit, it is possible to suppress variations in the current flowing through the illumination lamp due to variations in the oscillation frequency of the oscillation means. Thereby, it is possible to suppress an increase in special manufacturing management processes and mounted parts, and it is possible to reduce manufacturing costs.

  In the above configuration, the detection unit converts the detection current into a detection voltage and sends the detection voltage to the control circuit, and the control circuit includes a circuit that compares the detection voltage with a given reference voltage. The switching element may be turned on each time the oscillation signal rises, and when the detection voltage reaches the reference voltage, the switching element may be turned off.

  In the above configuration, the control circuit includes a reference current generation circuit that biases the oscillation means, the oscillation frequency of the oscillation means varies depending on the reference current value, and the adjustment circuit is configured to detect the detection voltage based on the reference current. There may be provided an offset voltage generation circuit for generating an offset voltage for offsetting.

  In the above configuration, the offset voltage generation circuit includes a bias current supply unit that supplies the reference current as a bias current, and an offset resistor through which the bias current flows, and is generated by the bias current and the offset resistor. The offset voltage may be added to the detection voltage.

  In the above configuration, the control circuit includes a reference current generating circuit for biasing the oscillating means, the oscillation frequency of the oscillating means varies depending on the reference current value, and the adjusting circuit is configured to change the reference voltage based on the reference current. May be provided.

  In the above-described configuration, the reference voltage generation circuit includes a plurality of diode-connected transistors stacked in series, the voltage generated by resistance division is buffered by the transistor, and the buffered voltage is connected to one or more diodes. The reference voltage may be generated by shifting with a transistor, and a circuit that links a bias current of a transistor that shifts the buffered voltage to the reference current may be provided.

  In the above configuration, the reference current is generated so as to be large when the oscillation frequency is high and small when the oscillation frequency is low, and the adjustment circuit has a short ON period of the switching element when the oscillation frequency is high. When the oscillation frequency is low, the switching element may be adjusted so that the ON period of the switching element becomes long.

  In the above configuration, the adjustment circuit may be configured to cancel the fluctuation of the oscillation frequency of the oscillation means with the dependence characteristic of the square of the current value of the detection current.

  In the above configuration, the control circuit includes a circuit that compares the detection voltage with a phase detection voltage that is obtained by rectifying the AC voltage, resistance-dividing, and smoothing the capacitance, and the control circuit includes the detection voltage. When the voltage reaches the smaller one of the reference voltage and the phase detection voltage, the switching element may be turned off. According to this configuration, it is possible to suppress variations (fluctuations) in the illuminance of the illumination lamp even when the dimming is performed by the phase control dimmer.

  The illumination power supply circuit described above is used in an illumination device that supplies current to an illumination lamp equipped with a light source that is lit with a direct current, such as LED and organic EL, and whose brightness (illuminance) is changed by turning on and off the switching element. May be.

  According to the present invention, it is possible to provide a lighting power supply circuit with less variation (variation) in illuminance by offsetting variation (variation) in the oscillation frequency of the oscillation signal of the oscillator by adjusting the current detection level of the switching element. .

It is a figure which shows an example of the power supply circuit for illumination concerning this invention. It is a figure which shows an example of the bias current generation circuit used for the power supply circuit for illumination shown in FIG. It is a figure which shows the other example of the power supply circuit for illumination concerning this invention. FIG. 4 is a diagram showing an example of a reference voltage generation circuit provided in the switching transistor control circuit shown in FIG. 3. It is a figure which shows the waveform of the supply current in the power supply circuit for illumination concerning this invention. It is a figure which shows the further another example of the power supply circuit for illumination concerning this invention. It is a figure which shows the further another example of the power supply circuit for illumination concerning this invention. It is a figure which shows an example of the conventional power supply circuit for illumination. It is a figure of the other example of the conventional power supply circuit for illumination. It is a timing chart which shows operation | movement of the switching transistor drive circuit in the conventional power supply device for illumination. 10B is a timing chart showing the operation of the switching transistor drive circuit when the reference voltage is lower than that in FIG. 10A. FIG. 10B is a timing chart showing the operation of the switching transistor drive circuit when driven by changing the oscillation frequency of the oscillator in the state of FIG. 10A. 11B is a timing chart showing the operation of the switching transistor drive circuit when the oscillation frequency is lower than that in FIG. 11A.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing an example of an illumination power supply circuit according to the present invention. In FIG. 1, the same parts as those of FIG. As shown in FIG. 1, the illumination power supply circuit A is a power supply circuit for supplying a direct current to an LED module 4 (illumination lamp) having a predetermined number of LEDs. The illumination power supply circuit A includes a rectifier circuit 2, a smoothing circuit 3, a coil L1, a freewheeling diode Df1, a switching transistor 5 (switching element), a current value detecting resistor Rs (detecting means), an offset generating resistor Rf, and a switching transistor control circuit. 6 (control circuit). The switching transistor control circuit 6 is an integrated circuit (IC). The switching transistor control circuit 6 includes a comparator 61, a power source 62, an oscillator 63 (oscillating means), and a flip-prop 64.

  The illumination power supply circuit A includes an offset voltage generation circuit Oj that is one of adjustment circuits including a bias current supply unit 60 and an offset generation resistor Rf. In the offset voltage generation circuit Oj, only the bias current supply unit 60 is formed inside the switching transistor control circuit 6. This is to prevent variations in the resistance value of the offset generation resistor Rf due to variations in the semiconductor process.

  The offset voltage generation circuit Oj is a circuit for offsetting the detection voltage converted by the current value detection resistor Rs. The offset voltage generation circuit Oj operates to add an offset voltage generated by the product of the bias current supplied from the bias current supply unit 60 and the resistance value of the offset generation resistor Rf to the detection voltage. For example, the switching transistor drive circuit 6 operates in the same manner as in FIG. 10A, and the voltage waveform a1 in FIG. 10A is offset upward by adding the offset voltage to the detection voltage. For example, when the offset voltage to be added is large, the difference between the voltage waveform a1 and the voltage waveform b1 is small, the time for the voltage waveform a1 to reach the voltage waveform b1 is shortened, and the ON period of the switching transistor 5 is shortened (duty duty). Becomes smaller). Conversely, when the offset voltage is small, the difference between the voltage waveform a1 and the voltage waveform b1 is large, the time for the voltage waveform a1 to reach the voltage waveform b1 becomes long, and the ON period of the switching transistor 5 becomes long (duty becomes large). ). That is, by offsetting the detection voltage, the minimum value of the detection level of the current value of the detection current (current value detection level) can be increased, and the difference between the reference voltage and the minimum detection level of the detection current can be reduced. The same effect can be obtained as reducing the reference voltage.

  The LED supply current flowing through the LED module 4 increases as the ON period of the switching transistor 5 increases. Therefore, when viewed as a lighting device, the LED supply current is bright when the offset voltage is small and dark when the offset voltage is large. That is, if the offset voltage is adjusted, the on / off duty of the switching transistor 5 (the length of the on period of the switching transistor 5) can be adjusted, and the LED supply current flowing through the LED module 4 can be adjusted. The offset voltage generation circuit Oj uses the fact that the LED supply current can be adjusted by changing the offset voltage, and thus varies (fluctuates) in the oscillation frequency (number of clocks) of the oscillation signal (clock pulse) output from the oscillator 63. In addition, by adjusting the bias current, variations in the LED supply current supplied to the LED module 4 are offset, and variations in the brightness characteristics of the lighting device are suppressed.

  Next, details of a bias current generation circuit that generates a bias current supplied from the bias current supply unit will be described. FIG. 2 is a diagram showing an example of a bias current generating circuit used in the illumination power supply circuit shown in FIG. The bias current generating circuit shown in FIG. 2 is configured inside the switching transistor control circuit 6 and includes a reference current generating circuit that generates a reference current Ic. Note that the bias current is linked to the reference current Ic.

  As shown in FIG. 2, the bias current generating circuit is composed of ten transistors Q1 to Q10 and four resistors R1 to R4. Transistors Q1 to Q8 and resistors R1 to R4 constitute an activation circuit and a reference current generation circuit. The bias current is linked with the reference current Ic generated by the reference current generation circuit.

  Transistors Q1-Q6 are npn transistors, and transistors Q7-Q10 are pnp transistors. Three diode-connected transistors Q1-Q3 are stacked, the collector of the transistor Q1 is connected to the resistor R1, and the base of the transistor Q3 is connected to the base of the transistor Q4. The emitter of the transistor Q3 is connected to the resistor R2.

  A current flows to the resistor R2 through the resistor R1 and a so-called diode-connected transistor Q1-Q3 in which the base and the collector are short-circuited, whereby a current is supplied to the base of the transistor Q4 and the transistor Q4 is turned on. When the transistor Q4 is turned on, the transistors Q5-Q6 and Q7-Q8 are turned on, and the reference current Ic is generated by the transistors Q5-Q6 and the resistor R3. The reference current Ic is a current that biases the oscillator 63 and a current that is a source of the bias current. More specifically, the emitter area ratio S of the transistors Q5 and Q6 (here, S = 10 because 10: 1) and the resistance value r3 of the resistor R3 are used, and the reference current value ic is {reference current value ic = VT (lnS ) / R3}. Note that VT is a general thermal voltage in a semiconductor process, and the thermal voltage VT is calculated by {VT = p / kT}. Here, p is an electric charge, k is a Boltzmann constant, T is an absolute temperature, and it is known that VT is about 26 mV at room temperature.

  From the above equation, the reference current value ic is determined by the resistance value r3 of the resistor R3. That is, when the resistance value r3 of the resistor R3 varies (fluctuates), the reference current value ic also varies (varies). In a normal semiconductor process, the resistance value has a variation (variation) of about 10% or more, and the variation (variation) in the reference current value ic is caused by the variation in the resistance value r3 of the resistor R3. .

  In the bias current generating circuit according to the present invention shown in FIG. 2, the transistors Q7 and Q8 are turned on, and at the same time, the transistors Q9 and Q10 are turned on. At this time, since the bases of the transistors Q7 to Q10 are connected, the bases of the transistors Q7 to Q10 have the same voltage value. Thereby, the current between the emitters and collectors of the transistors Q9 and Q10 becomes the same current as the current between the emitters and collectors of the transistors Q7 and Q8, that is, the reference current Ic (the current flowing through the transistor Q10 is a bias current).

  The oscillator 63 is biased with the reference current Ic, and the oscillation frequency of the oscillator 63 is affected by variations (fluctuations) in the reference current Ic. Since the response characteristics of the oscillator 63 improve as the reference current Ic increases, the oscillation frequency (number of clocks) increases. Conversely, when the reference current Ic decreases, the oscillation frequency (number of clocks) of the oscillator 63 decreases. As described above, the LED supply current supplied to the LED module 4 increases when the oscillation frequency (number of clocks) of the oscillator 63 is high, and the LED module becomes bright, and the LED module becomes dark when the oscillation frequency is low.

  In the bias current generation circuit according to the present invention shown in FIG. 2, the same reference current Ic as the reference current Ic for biasing the oscillator 63 is used as the bias current supplied from the bias current supply unit 60. When the reference current value ic increases, the oscillation frequency of the oscillation signal output from the oscillator 63 increases. On the other hand, since the bias current value supplied from the bias current supply unit 60 is increased, the offset voltage for offsetting the detection voltage is also increased, and the ON period of the switching transistor 5 is shortened.

  That is, as the reference current value ic increases, the oscillation frequency of the oscillator 63 increases, and the number of times the switching transistor 5 is turned on increases. However, when the offset voltage increases, the ON period of the switching transistor 5 decreases. That is, the increase in the number of times the switching transistor 5 is turned on due to the oscillation frequency of the oscillator 63 is offset by the shortening of the on period. From this, the variation (variation) in the current value of the LED supply current supplied to the LED module 4 due to the variation (variation) in the semiconductor process (variation in resistance R3) when manufacturing the switching transistor drive circuit 6, that is, It is possible to suppress variations (fluctuations) in the brightness characteristics of the lighting device. The offset voltage generation circuit shown in FIGS. 1 and 2 is an example, and the present invention is not limited to this. A circuit that can offset the detection voltage in accordance with the current for biasing the oscillator 63 can be widely used.

(Second Embodiment)
Another example of the illumination power supply circuit according to the present invention will be described with reference to the drawings. FIG. 3 is a diagram showing another example of the illumination power supply circuit according to the present invention. In FIG. 3, the same parts as those in FIG. 9 are denoted by the same reference numerals, and detailed description of the same parts is omitted.

  As shown in FIG. 3, the illumination power supply circuit B is one of adjustment circuits in the switching transistor control circuit 6 </ b> B, and includes a reference voltage generation circuit 65 that generates a reference voltage input to the comparator 61. The reference voltage generation circuit 65 is also configured inside the switching transistor control circuit 6B.

  FIG. 4 is a diagram showing an example of a reference voltage generation circuit provided in the switching transistor control circuit shown in FIG. The reference voltage generation circuit 65 shown in FIG. 4 has a circuit having the same configuration as the bias current generation circuit shown in FIG. 2, and detailed description thereof is omitted. As shown in FIG. 4, the reference voltage generation circuit 65 has a configuration including ten transistors Q11 to Q20 and one resistor R5. In the reference voltage generating circuit 65, the reference voltage is generated by accumulating the five base-emitter voltages of the transistors Q13 to Q17, buffering the voltage with the transistor Q18, and further shifting with the transistors Q19 and Q20. The transistors Q19 and Q20 are biased with a bias current having the same current value as the reference current Ic for biasing the oscillator 63 by a current mirror circuit composed of the transistors Q11 and Q12.

  The voltage between the base and emitter of the transistor depends on the collector current. When the collector current increases, the voltage between the base and emitter of the transistor also increases. That is, when the reference current Ic increases, the collector current of the transistors Q18-Q20 increases, and the base-emitter voltage of the transistors Q18-Q20 increases. Therefore, when the reference current value ic increases, the shift amount of the transistor Q18 with respect to the base voltage increases, and the reference voltage decreases.

  As the reference current Ic increases, the oscillation frequency (number of clocks) of the oscillator 63 increases and the reference voltage decreases, so that the number of times the switching transistor 5 is turned on increases, but the ON period decreases. On the other hand, when the reference current Ic decreases, the oscillation frequency (number of clocks) of the oscillator 63 decreases and the reference voltage increases, so that the number of times the switching transistor 5 is turned on decreases while the on period increases. Thereby, the average of the LED supply current supplied to the LED module 4 is constant or substantially constant even if the oscillation frequency varies.

  As a result, even if the reference current Ic (resistor R3) varies (even if it fluctuates), the average variation (variation) in the LED supply current flowing through the LED module 4 can be suppressed, and variation in the brightness characteristics of the lighting device ( Fluctuation). Note that the reference voltage generation circuit shown in FIG. 4 is merely an example, and the present invention is not limited to this configuration. A circuit that can adjust the reference voltage in accordance with the current that biases the oscillator 63 can be widely used. It is.

(Third embodiment)
Still another example of the illumination power supply circuit according to the present invention will be described with reference to the drawings. FIG. 5 is a diagram showing a waveform of a supply current in the illumination power supply circuit according to the present invention. FIG. 5 also shows an overview of the LED module 4, the coil L1, the switching transistor 5, and the current value detection resistor in order to show the voltage, resistance, impedance, and the like of each part.

  FIG. 5 shows the change in the LED supply current supplied to the LED module 4 over time. As shown in FIG. 5, the current waveform of the LED supply current supplied to the LED module 4 is a sawtooth waveform. The brightness of the lighting device depends on the LED supply current supplied to the LED module 4. That is, the brightness of the lighting device depends on the LED drive current ILED, which is the average of the LED supply current, because the LED supply current has a sawtooth waveform.

  In FIG. 5, Ton is a period during which the switching transistor 5 is on, Toff is a period during which the switching transistor 5 is off, and Tres is until the switching transistor 5 is turned off to release energy stored in the coil to zero. Is the period. Tc is the period of the current waveform (period from the on timing to the next on timing) and is represented by the reciprocal of the oscillation frequency fc of the oscillation signal output from the oscillator 63.

また、オフ期間の長さＴｏｆｆは数２に示すとおりになる。

１周期間の電流値をＴｏｎとＴｒｅｓの２つの三角形面積として算出し、周期Ｔｃで割ることで、ＬＥＤ供給電流の平均であるＬＥＤ駆動電流ＩＬＥＤを得る。ＩＬＥＤの算出式を数３に示す。

As shown in the circuit diagram of FIG. 5, the voltage (supply voltage) supplied to the LED module 4 is VB, the total forward voltage of the LED module 4 is VF, the inductance of the coil L1 is L, the peak of the LED supply current When the value is Ipk, the length Ton of the on period is as shown in Equation 1.

Further, the length Toff of the off period is as shown in Equation 2.

The current value for one period is calculated as two triangular areas of Ton and Tres, and divided by the period Tc to obtain the LED drive current ILED that is the average of the LED supply current. The calculation formula of ILED is shown in Equation 3.

  From Equation 3, the LED drive current ILED supplied to the LED module 4 depends on the oscillation frequency fc of the oscillator 63 and the square of the peak value Ipk of the LED supply current. Therefore, if the LED supply current (detected voltage detected by the current value detection resistor Rs) is canceled out by the square dependence characteristic with respect to the variation (fluctuation) of the oscillation frequency fc, the oscillation of the oscillator 63 will occur. It is possible to correct frequency variations (variations) with high accuracy. From this, the variation in the illuminance of the LED module 4 can be accurately reduced by selecting the elements constituting the circuit so that the LED supply current is canceled by the square dependence characteristic.

(Fourth embodiment)
Still another example of the illumination power supply circuit according to the present invention will be described with reference to the drawings. FIG. 6 is a diagram showing still another example of the illumination power supply circuit according to the present invention. The illumination power supply circuit C shown in FIG. 6 includes a dimmer 11 between the AC power supply 1 and the rectifier circuit 2. In addition, a dimmer phase detection circuit Fj that converts the current flowing through the rectifier circuit 2 into a voltage and detects the phase of the dimmer is provided. Furthermore, a switching transistor control circuit 6C is provided, and a dimmer comparator 66 is added inside the switching transistor control circuit 6C. The other parts have the same configuration as that of the illumination power supply circuit A shown in FIG. 1 and are given the same reference numerals, and detailed description of the same parts is omitted.

  The dimmer 11 is a well-known phase control type dimmer. For example, as described in Japanese Patent Application Laid-Open No. 2010-212267, the phase control type dimmer has a phase angle with an AC voltage output from the AC power source 1 by switching elements (typically thyristor elements or triac elements). The power supply to the LED module 4 is controlled by turning on the LED, and the dimming control of the LED module 4 can be easily performed with a single volume element. The average value of the current adjusted by the dimmer 11 and smoothed by the smoothing circuit 3 is determined by the phase angle at which the switching element of the dimmer 11 is turned on. Therefore, the dimmer phase detection circuit Fj is used to detect the phase angle of the dimmer as a phase detection voltage and detect the LED drive current value supplied to the LED module 4. The dimmer phase detection circuit Fj includes two resistors Rf1 and Rf2 and a capacitor Cf1. The dimmer phase detection circuit Fj detects a voltage (phase detection voltage) that is resistance-divided by the resistors Rf1 and Rf2 and smoothed by the capacitor Cf1 from the current rectified by the rectifier circuit 2. The detected phase detection voltage is input to the dimmer comparator 66 as a threshold voltage.

  The dimmer comparator 66 of the switching transistor control circuit 6C detects the current value detection resistor Rs, compares the detection voltage offset by the offset voltage calculated by the bias current and the offset resistance, and compares the threshold voltage with the offset voltage. When the detected voltage is lower than the threshold voltage, a low level is output. When the offset detection voltage reaches the threshold voltage, a high level is output. The output of the dimmer comparator 66 is input to the reset of the flip-flop 64.

  As shown in FIG. 5, when either the comparator 61 or the dimmer comparator 66 outputs a high level, the high level is input to the reset of the flip-flop 64. In the switching transistor control circuit 6C, the variation in the oscillation frequency of the oscillator 63 is offset by the bias current and the offset voltage. Further, by using the dimmer comparator 66, it is possible to control the on / off of the switching transistor 5 at the same timing as the phase angle of the dimmer 11. As a result, it is possible to suppress variations in brightness characteristics of the lighting device due to variations (variations) in the oscillator caused by variations in the semiconductor process of the switching transistor control circuit 6C, and accurately respond to dimming of the dimmer. The lighting device (LED module) can be turned on with the brightness.

  Since the comparator 61 operates to control (limit) the maximum value of the LED supply current supplied to the LED module 4, the maximum brightness of the lighting device is determined. On the other hand, the dimmer comparator 66 varies the brightness of the lighting device in accordance with the dimming operation by the dimmer 11, that is, controls the lighting operation up to the maximum brightness. From the above, the resistance values of the resistors Rf1 and Rf2 and the capacitance of the capacitor Cf1 are determined so that the threshold voltage of the dimmer comparator 66 is lower than the reference voltage of the comparator 61.

  In the present embodiment, the switching transistor control circuit 6C includes a bias current generation circuit, and the illumination power supply device C having a configuration including an offset voltage generation circuit as an adjustment circuit is described as an example. A configuration including a reference voltage generation circuit may be used.

(Fifth embodiment)
Still another example of the illumination power supply circuit according to the present invention will be described with reference to the drawings. FIG. 7 is a diagram showing still another example of the illumination power supply circuit according to the present invention. The illumination power supply circuit D shown in FIG. 7 is an insulation type, and the coil connected to the switching transistor 5 is a transformer Tr, so that the primary power supply and the secondary LED module 4 can be insulated. Is possible.

  Except for the LED module 4 and the transformer Tr, the configurations described in the above-described embodiments can be used. The primary coil Lt1 of the transformer Tr can also store energy, and after the switching transistor 5 is turned off in the illumination power supply circuit D, the energy stored in the primary coil Lt1 becomes zero. Until then, an electromotive force is generated in the secondary coil Lt2. Thereby, a current is supplied to the LED module 4 until the switching transistor 5 is turned off and the energy stored in the primary coil Lt1 becomes zero. In the illumination power supply circuit D, a Schottky diode Ds1 is attached to the LED module 4 to prevent the current from flowing backward.

  As described above, by using the illumination power supply circuit shown in each embodiment, the illumination illuminance (brightness) due to the variation (fluctuation) in the oscillation frequency (number of clocks) of the oscillator, which is caused by the variation during the manufacturing of the switching transistor control circuit, Variation can be suppressed.

  Further, as the above-described switching transistor, for example, a transistor that is turned on / off by a signal from a switching transistor control circuit such as a bipolar transistor, a MOS transistor, a MOSFET, or an IGBT can be widely used. In addition to transistors, switching elements that can be switched on and off by receiving signals can be widely employed.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this content. The embodiments of the present invention can be variously modified without departing from the spirit of the invention.

  The illumination power supply circuit according to the present invention can be used in an illumination device that adjusts illuminance (brightness) by lighting with a direct current such as an LED or an organic EL and changing an on / off duty.

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectifier circuit 3 Smoothing circuit 4 LED module 5 Switching transistor 6 Switching transistor control circuit (IC)
60 Bias Current Supply Unit 61 Comparator 62 Power Supply 63 Oscillator 64 Flip Flop (SR Type)
65 Reference voltage generation circuit 66 Dimmer comparator Rs Current value detection resistor Rf Offset generation resistor L1 Coils Q1 to Q6, Q11 to Q20 Transistors (npn type)
Q7 to Q10 transistors (pnp type)
R1-R5 resistance

Claims (11)

A lighting power supply circuit that rectifies and smoothes an alternating voltage and supplies a direct current generated by smoothing to an illumination lamp,
A coil through which the direct current flows;
At least a free-wheeling diode connected in antiparallel with the coil;
A switching element that is connected in series with the coil and adjusts the current supplied to the illumination lamp;
Detecting means for detecting a current flowing through the switching element;
A control circuit for controlling on / off of the switching element based on an oscillation signal of an oscillation means provided inside and a value of a detection current detected by the detection means;
An illumination power supply circuit comprising: an adjustment circuit that adjusts a current value detection level of the detection current in accordance with a change in an oscillation frequency of an oscillation signal of the oscillation means. The detection means converts the detection current into a detection voltage and sends it to the control circuit,
The control circuit includes a circuit that compares the detection voltage with a given reference voltage, and turns on the switching element at each rising edge of the oscillation signal, and the detection voltage reaches the reference voltage. The power supply circuit for illumination according to claim 1, wherein the switching element is turned off. The control circuit includes a reference current generating circuit that biases the oscillating means, and the oscillation frequency of the oscillating means varies depending on the reference current value generated by the reference current generating circuit,
The illumination power supply circuit according to claim 2, wherein the adjustment circuit includes an offset voltage generation circuit that generates an offset voltage for offsetting the detection voltage based on the reference current. The offset voltage generation circuit includes a bias current supply unit that supplies the reference current as a bias current;
An offset resistor through which the bias current flows,
The illumination power supply circuit according to claim 3, wherein an offset voltage generated by the bias current and the offset resistor is added to the detection voltage. The control circuit includes a reference current generating circuit that biases the oscillating means, and the oscillation frequency of the oscillating means varies depending on the reference current value generated by the reference current generating circuit,
The illumination power supply circuit according to claim 2, wherein the adjustment circuit includes a reference voltage generation circuit that generates the reference voltage based on the reference current. The reference voltage generating circuit stacks a plurality of diode-connected transistors in series and divides the resistance and buffers the voltage generated by the transistor, and the buffered voltage is converted into one or a plurality of diode-connected transistors. The reference voltage is generated by shifting,
6. The illumination power supply circuit according to claim 5, further comprising a circuit that links a bias current of a transistor that shifts the buffered voltage with the reference current.   The adjustment circuit adjusts the ON period of the switching element so that the ON period of the switching element is short when the oscillation frequency is high and the ON period of the switching element is long when the oscillation frequency is low. The illumination power supply circuit according to claim 6.   The illumination power supply circuit according to any one of claims 2 to 7, wherein the adjustment circuit is a circuit that cancels a variation in an oscillation frequency of the oscillation means with a dependence characteristic of a square of the current value of the detection current. The control circuit includes a circuit that compares the detection voltage with a phase detection voltage that is rectified and resistance-divided by the AC voltage and smoothed by a capacitor, and
The power supply for illumination according to any one of claims 2 to 8, wherein the control circuit turns off the switching element when the detection voltage reaches the smaller one of the reference voltage and the phase detection voltage. circuit.   The illumination power supply circuit according to claim 1, wherein a current is supplied to an illumination lamp using an LED as a light source.   11. An illumination device using the illumination power supply circuit according to claim 1.

Images