JPH07274522A - Load control device - Google Patents

Abstract

PURPOSE:To improve an overall circuit efficiency by reducing a power loss generated in an input part, in the case of low power supply voltage as compared with output voltage. CONSTITUTION:In a load control device comprising a DC power supply 1, high frequency converter circuit 2 converting voltage of this DC power supply 1 into square wave voltage of high frequency, transformer converting an output of the high frequency converter circuit 2 into voltage, rectifier circuit rectifying an output of the transformer, inverter circuit connected to an output of the rectifier circuit and a load connected to an output of the inverter circuit, a current limiting element for limiting a current of the load is connected between the transformer and the rectifier circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load control device for controlling a load by using a semiconductor switching element, and is suitable for lighting a discharge lamp, for example.

[0002]

2. Description of the Related Art Conventionally, a discharge lamp lighting device as shown in FIG. 16 has been known. The AC power supply 1 is converted into a sine wave high frequency voltage by the high frequency conversion circuit 2a and applied to the primary side of the transformer T ₁ . The high-frequency voltage up or steps down by transformer T _1, a high frequency voltage obtained on the secondary side rectifying and smoothing by the rectification circuit DB ₁ and the capacitor C _1, a full-bridge DC voltage obtained in the capacitor C ₁ the four switching elements S ₁ to S ₄ of the inverter 4 converts the square wave voltage of low frequency, is intended to be turned square wave is applied to the discharge lamp 3. This structure is disclosed in JP-A-56
No. 5,0092,9.

In this conventional example, the high frequency conversion circuit 2 is composed of a push-pull inverter, and the transformer T
_A circuit composed of a switching element, a capacitor, an inductance element and the like is connected to the primary side of ₁ . In this configuration, instead of the AC power supply 1, the power supply voltage is low DC power source (e.g., DC24V and DC12V) In the case of using, when supplying the discharge lamp 3 similar output to the primary side of the transformer T ₁ The flowing current becomes very large, the power loss of the capacitor, the inductance element, etc. increases, the parts become large, and the cost becomes high. In addition, the circuit efficiency of the entire device is deteriorated, and the size of the entire device is increased.

That is, in the circuit of FIG. 16, a current limiting element is provided inside the high frequency conversion circuit 2 in order to stably maintain the lighting of the discharge lamp 3 and to control the supply power thereof. A large amount of current flows through the element, which is the capacitor or the inductance element. In particular, when the turns ratio of the transformer T ₁ becomes large (for example, when the input voltage is 12V,
When the output voltage is 100 V), the primary current of the transformer T ₁ increases and the loss of the current limiting element increases. Japanese Patent Laid-Open No. 2-2
The 88197 JP, but connecting the current limiting element to the secondary side of the transformer T _1, the circuit of the primary side and by applying a sine waveform to the transformer T ₁ by resonance, when the power supply voltage is low device , The loss due to this primary circuit is still large. Further, when controlling the load, frequency or on-duty control is generally used, but the control range is narrowed due to reasons such as setting the frequency or on-duty control range in consideration of the resonance frequency. There are many restrictions on circuit design.

FIG. 17 shows a method of supplying power to the control circuit 7 in the conventional load control device. In the figure,
Reference numeral 1 is a DC power supply, 2 is a high frequency conversion circuit, 3 is a load, 4 is a low frequency conversion circuit, 7 is a control circuit, 8 is an input filter circuit, and T ₁ is a transformer. The DC power supply 1 is converted into a high frequency voltage by the high frequency conversion circuit 2 via the input filter circuit 8 and boosted by the transformer T ₁ , and the high frequency voltage is converted to a low frequency (several tens Hz to several hundreds Hz) by the low frequency conversion circuit 4. ), And supplies electric power to the load 3. When the output of the transformer T ₁ is high voltage, the transformer T _1
Although insulated by ₁ , the control circuit 7 needs to be insulated from the low frequency conversion circuit 4 in order to drive the switching element of the low frequency conversion circuit 4. However, in this case, it is difficult to accurately detect the state of the load 3, because it is inaccurate to send a signal while insulating by using a photocoupler. In addition, there were many restrictions in terms of size and cost in design. In addition, the high frequency conversion circuit 2 has a high frequency (several hundred K
Becomes a Hz~ number MHz), the temperature rise of the electrolytic capacitor C ₈ by the charge and discharge current of the electrolytic capacitor C ₈ is increased, there is a problem in terms of service life.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to convert a DC power supply into a high frequency, convert the voltage with a transformer, and output the transformer. In a load control device that rectifies the current and supplies it to the load as a low-frequency output, when the power supply voltage is lower than the output voltage, it is possible to reduce the power loss that occurs in the input section and improve the overall circuit efficiency. is there. Another object of the present invention is to improve the safety of the load control device in which the primary side and the secondary side are separated by a transformer, by supplying the power source of the secondary side control circuit from the transformer. It is to increase the temperature and suppress the heat generation of the capacitor connected to the input section.

[0007]

FIG. 1 shows the basic configuration of the present invention.
Shown in. In the figure, 1 is a DC power supply, 2 is a high frequency conversion circuit, and T
₁ is a transformer, 5 is a current limiting circuit, DB1 is a rectifying circuit, 4 is an inverter circuit, and 3 is a load. In the current limiting circuit 5, L ₁ is an inductance element and C ₂ is a capacitor. The capacitor C ₂ may be connected for waveform shaping or may be omitted. A capacitor C ₁ is connected in parallel with the output of the rectifier circuit DB ₁ . The feature of the present invention is that a rectangular wave voltage is applied to the primary side of the transformer T ₁ by a switching element in the high frequency conversion circuit 2,
The secondary side of the transformer T ₁ is transformer T ₁ and the rectifier circuit D
The point is that the current limiting circuit 5 of the load 3 is provided between B ₁ .

[0008]

According to the present invention, the primary side of the transformer T ₁ is
Since the rectangular wave voltage is applied by the switching element in the high frequency conversion circuit 2, even when the voltage of the DC power supply 1 is low,
The loss of the current limiting element due to the current flowing through the primary side of the transformer T ₁ can be reduced. Further, the secondary side of the transformer T ₁ is limiting circuit of the transformer T ₁ and the load between the rectifier circuit DB ₁ 3 5
Since the inductance element L ₁ of the current limiting circuit 5 is required to flow a small amount of current after boosting because copper loss is reduced, a small component can be used. In the conventional example, since the current limiting element is on the primary side, it is not possible to deal with it only by the turns ratio of the transformer T ₁ , and the design change becomes complicated. However, in the present invention, the transformer T ₁ allows the primary side and the secondary side to be changed. Insulation is easy, and even specifications with different power supply voltages can be dealt with by changing the winding ratio of the transformer T ₁ , and the variety of products can be easily expanded.

[0009]

FIG. 2 is a circuit diagram of the first embodiment of the present invention.
The present embodiment more specifically shows the high frequency conversion circuit 2 of FIG. 1, and uses a high frequency conversion circuit having a half-bridge structure. In the figure, Q ₁ and Q ₂ are transistors,
D ₁ and D ₂ are diodes, and C ₄ and C ₅ are capacitors. The transistors Q ₁ and Q ₂ are alternately turned on and off, whereby a voltage half that of the DC power supply 1 is applied in a rectangular wave shape to the primary side of the transformer T ₁ . This rectangular wave voltage is boosted by the transformer T ₁ and electric power is sent to the load 3 via the current limiting circuit 5. The operations of the rectifier circuit DB ₁ , the capacitor C ₃ , the inverter circuit 4, etc. are the same as in the conventional example of FIG.

3 to 5 are circuit diagrams of essential parts of the second to fourth embodiments of the present invention. In the embodiment of FIG. 3, the high frequency conversion circuit 2 has a full bridge structure, and the structure of the secondary side of the transformer T ₁ is the same as that of FIG. In the figure, Q ₃ to Q ₆ are transistors, D ₃ to D ₆ are diodes. Transistor Q
₃ , Q ₆ and transistors Q ₄ , Q ₅ are alternately turned on and off, and transistors Q ₃ , Q ₆ are turned on and transistor Q ₆ is turned on.
_{When 4} and Q ₅ are off, the voltage of the DC power supply 1 is applied to the primary side of the transformer T ₁ , and when the transistors Q ₃ and Q ₆ are off and the transistors Q ₄ and Q ₅ are on, the DC power supply 1 is Is applied with reverse polarity to the primary side of the transformer T ₁ . In the embodiment of FIG. 4, the high frequency conversion circuit 2 has a modified half bridge configuration, and the configuration of the secondary side of the transformer T ₁ is the same as that of FIG. In the figure, Q ₁ and Q ₂ are transistors and D
₁ and D ₂ are diodes, and C ₆ is a capacitor. The transistors Q ₁ and Q ₂ are alternately turned on and off, and the AC component of the rectangular wave voltage generated across the transistor Q ₂ is supplied to the primary side of the transformer T ₁ via the capacitor C ₆ . In the embodiment of FIG. 5, the high frequency conversion circuit 2 has a push-pull configuration, and the secondary side configuration of the transformer T ₁ is the same as that of FIG. In the figure, Q ₁ and Q ₂ are transistors. The transistors Q ₁ and Q ₂ are alternately turned on and off, and the voltage of the DC power supply 1 is alternately applied with reverse polarity to the primary side of the transformer T ₁ . In any of the embodiments shown in FIGS. 3 to 5, the current limiting circuit 5 is provided on the secondary side of the transformer T ₁ as in the first embodiment.

FIG. 6 is a circuit diagram of the fifth embodiment of the present invention. In the figure, 6 is a starting circuit, 7 is a control circuit, 8 is a voltage detection unit, SW is a switch, CT is a current detection unit, and DR _{1 to} DR
₃ is a drive circuit and 3 is a high pressure discharge lamp. When the switch SW is turned on, the control circuit 7, the high frequency conversion circuit 2 and the inverter circuit 4 operate, the igniter IG of the starting circuit 6 generates a high voltage pulse, and the pulse transformer PT applies the high voltage pulse to the discharge lamp 3. And start it. The voltage across the discharge lamp 3 is substantially detected by the voltage detector 8, the current is detected by the current detector CT, and the switching frequency fs or the on-duty of the high frequency conversion circuit 2 is controlled according to the detected amount. The electric power is supplied to the discharge lamp 3. The switching frequency fs is, for example, several tens of KHz.
Several hundred KHz, the frequency of the inverter circuit 4 consisting of a switching element S ₁ to S ₄ is, 50 Hz to several hundreds Hz is preferred. No current limiting device is connected to the primary side of the transformer T ₁ ,
The inductance element L ₁ on the secondary side has that function.
The high voltage pulse voltage of the capacitor C ₇ is the inverter circuit 4
The closed circuit is formed so that it is not applied to the. The output of the transformer T ₁ is a rectangular wave high frequency voltage, and the rectifier circuit D
The discharge lamp 3 is rectified by B ₁ and smoothed by the capacitor C ₁ , and a low frequency voltage containing almost no high frequency is applied to the discharge lamp 3 so that the discharge lamp 3 is lit stably. This low frequency is determined by the switching frequency of the inverter circuit 4.

Next, the invention described in claim 4 will be described. FIG. 7 shows a power supply system for the control units 7a and 7b according to the present invention. The feature of the present invention is that the transformer T ₁
The primary side of the control unit 7a, is powered from the main power source 1, the control unit 7b of the secondary side of the transformer T ₁ is transformer T
It is configured to receive power from ₁ . Therefore, when the power is turned on, first, the control unit 7a and the high frequency conversion circuit 2 operate, the voltage is applied to the transformer T ₁ , then the control unit 7b operates and the low frequency conversion circuit 4 operates, The load 3 is controlled. With this configuration, the primary side and the secondary side of the transformer T ₁ are completely insulated, and it is safe even if the secondary side of the transformer T ₁ has a high voltage. In addition, the low frequency conversion circuit 4 and the control unit 7b detect the load state,
Since the load 3 is controlled according to it, the accuracy is good. The control unit 7b generates a control power supply from the output of the transformer T ₁ and generates a control signal, and detects the drive unit of the switching element in the low frequency conversion circuit 4 and the load current / voltage. Section, a comparison circuit section for comparing the detected value and the reference value, and the like.

FIG. 8 shows an embodiment in which FIG. 7 is further embodied. The high frequency output of the transformer T ₁ is rectified by the rectifier circuit DB ₁ , and the inductance element L ₁ and the switching element S ₇ ,
A low-frequency inverter circuit 4 for polarity reversal that is boosted by a boost chopper circuit composed of a diode D ₇ and a capacitor C _1.
A low frequency voltage is supplied to the load 3a via a. The low-frequency inverter circuit 4a alternates the output voltage of the boost chopper circuit at a low frequency of several hundred Hz and applies it to the load 3a.
Control unit 7b detects the state of the load 3a, controls the on-duty of the switching element S _7. Control unit 7a will be may be control the voltage applied to the transformer T _1, separates the primary side and the secondary side of the transformer T _1, and it is accurately controllable. The load 3a is a high pressure discharge lamp, and is a discharge lamp lighting device that performs so-called rectangular wave lighting.

Next, the invention described in claim 6 will be described. FIG. 9 shows a main configuration of the present invention. A capacitor C ₉ through which a high-frequency current flows is connected to the input part of the high-frequency conversion circuit 2, and a capacitor C ₁₀ and an inductance element L ₃ are provided to back up the DC power supply 1 when there is an instantaneous voltage drop or instantaneous voltage drop. The series circuit is connected. This is intended to smooth or reduce the high frequency component flowing through the capacitor C ₁₀ . Capacitance of the capacitor C ₉ is sufficiently smaller capacity than the capacity of the capacitor C _10, using a ceramic capacitor or a film capacitor, it may be used an electrolytic capacitor in the capacitor C _10.

FIG. 10 shows a concrete example of the present invention.
A filter circuit 8 is provided in parallel with the capacitor C ₁₀ .
The function of the inductor L _{3 in} FIG. 9 is substituted for the noise filter transformer NF. The high frequency conversion circuit 2 converts a DC voltage into a high frequency voltage. This high frequency voltage is boosted by the transformer T ₁ , and the inverter circuit 4 converts the high frequency voltage into a direct current voltage and further into a lower frequency to light the load 3a. The load 3a is made of a fluorescent lamp, and the high frequency conversion circuit 2 is converted from several hundred KHz to several MHz and the inverter circuit 4 is converted into several tens KHz to light the load 3a from the viewpoint of luminous efficiency and noise of the fluorescent lamp. preferable. The high frequency conversion circuit 2 has a high frequency because of the miniaturization of the current limiting element.

FIG. 11 is an embodiment of the invention described in claim 6.
It is a circuit diagram which shows an example. The configuration of the input section is the same as that shown in FIG.
It is similar to the example. The load 3a is a high pressure discharge lamp, and has a rectangular shape.
It is a lighting device that lights in waves. The state of the load 3a is
Road DB₁Is detected at the input part of, and the load voltage is
Transformer T₂The load current by the current transformer CT
Detected by. The control unit 7a outputs the detection signal to the terminal
Input from a, b and c to control the high frequency conversion circuit 2
To do. The low frequency conversion circuit 4 includes a control unit 7b for low frequency driving.
Works by. A in the figure₁, A₂Is an AND circuit, N₁
Is an inverting circuit (inverter). PT₁, PT₂Is
Ruth trans, DR₁~ DR_FourIs the drive circuit, S₁~
S_FourIs a switching element. AND circuit A₁, A₂
Low frequency signal X and high frequency signal Y are input to
Low frequency signal X is switching element S₁, S_FourOn
Switching element S₂, S₃Alternating on at low frequencies
The high frequency signal Y is used for the pulse transformer P.
T₁, PT₂By operating the pulse transformer at high frequency.
PT₁, PT₂Is small, and primary side and secondary side are insulated
It is what makes me. Pulse transformer PT₁When works
Kiha (AND circuit A ₁When the output of is a high frequency signal Y),
Pulse transformer PT₁Rectifier circuit for high frequency voltage on the secondary side of
DB₁Rectified by, switching element S₁Between terminals d and e
Apply a drive voltage to the switch to turn it on and
Child S₁, S_FourOn state for low frequency half cycle
Let it continue. Drive circuit DR₁~ DR_FourCapacitors
Is a pulse transformer PT₁Of the high frequency of the terminal d,
A DC voltage is applied between e. AND circuit A₁of
When the output signal becomes zero, pulse transformer PT₁Works
Stop the drive circuit DR₁When the transistor is on
And discharges the electric charge between the terminals d and e,
Q₁Turns off. Switching element Q_FourAlso about
It is like. In the next half cycle, the switching element
Q₂, Q₃Turns on.

FIG. 11 shows a circuit embodying the basic example of FIG. 9. For example, as a power supply and signal generation system of the control unit 7b for low frequency driving, a configuration like the control unit 7b of FIG. 8 is used. May be. Since the low-frequency drive circuit has traditionally been a method of insulation driving with a photocoupler, there are restrictions on the performance of the photocoupler, and even when a pulse transformer is used, it is operated at the low frequency as it is. Although it is a large-sized pulse transformer, in the present invention, since the pulse transformers PT1 and PT2 are operated at a high frequency, the size is reduced.

FIG. 12 shows another embodiment of the drive circuit for driving the low frequency conversion circuit 4 shown in FIG. 12
As described above, when a high-voltage discharge lamp is used as the load 3a, a circuit including a parallel capacitor Cp and a series inductor Ls is added so that the high-voltage pulse voltage generated from the starting igniter circuit 6 is not applied to the inverter circuit. .
At this time, the switching elements S ₁ to
The switching operation of S ₄ is as shown in FIG. 13, and when the output polarity is switched, after turning off all the elements that were on until then, one of the elements that must be turned on first After turning on for a certain set time Td,
It is necessary to provide a time difference such that the other element is turned on. Therefore, of the drive circuits of the two switching elements that perform on / off operation in pairs, one of the off signals is transmitted to the switching element as it is, and the on signal is delayed for a certain set time, A delay circuit 9 for transmitting to the switching element is provided. The delay circuit 9 is inserted between the circuit for generating the drive signal and the control terminal of the switching element (for example, the gate electrode in the case of FET). For the other switching element,
The circuit for generating the drive signal may be directly connected to the control terminal of the switching element.

As an example of the delay circuit, for example, as shown in FIG. 14, a circuit composed of a resistor Rd, a capacitor Cd and a diode Ds is used. In this circuit, the ON signal is delayed by the integrating circuit composed of the resistor Rd and the capacitor Cd, and the OFF signal is rapidly transmitted through the diode Ds. Besides, as shown in FIG. 15, a delay circuit using a voltage input type transistor such as a MOSFET may be used. When the input voltage of the delay circuit is low, both the main switching element and the transistors Qd ₁ and Qd _{2 of the} delay circuit are turned off. Immediately after the voltage equal to or higher than the ON voltage of the main switching element is applied to the input of the delay circuit, the transistor Qd ₁ remains OFF, so that the drive signal is not transmitted to the main switching element and does not turn ON. Through resistor Rd _1, charges the capacitor Cd, the voltage of the capacitor Cd is exceeds the ON voltage of the transistor Qd _2, transistor Qd ₂ is turned on. When the transistor Qd ₂ turns on, the transistor Qd ₁ turns on, the drive signal is transmitted to the main switching element, and the main switching element turns on. When the input of the delay circuit drops to the off voltage of the main switching element, the diode Ds
To rapidly transmit the OFF signal to the main switching element. Also, the transistors Qd ₁ and Qd ₂ are turned off.

[0020]

According to the present invention, the output of the high frequency conversion circuit for converting the voltage of the DC power supply into the high frequency rectangular wave voltage is voltage-converted by the transformer, and the output is connected to the load through the rectifier circuit and the inverter circuit. In the load control device,
A current limiting element that limits the current of the load is connected between the transformer and the rectifier circuit, and the discharge lamp is stabilized without a substantial current limiting element on the primary side of the transformer, so that power loss is reduced. There is an effect that it is possible to provide a highly efficient load control device that reduces the load. In addition, the current limiting element
Since it is operated at the frequency of the high-frequency conversion circuit and is connected to a circuit portion with a small current, there is an effect that copper loss can be reduced and the inductance element can be downsized. Also, if the control power supply for the circuit configured on the secondary side of the transformer is obtained from the secondary side of the transformer, the primary side and the secondary side of the transformer can be reliably insulated, and the electric shock on the output side can be ensured. It is possible to provide a safe load control device for the above. Further, since the control in which the secondary side operates after the primary side starts moving can be automatically performed, a voltage is not applied to the load when it is unsafe at power-on, and safe operation can be realized. Further, even if the distance between the primary side and the secondary side is long, since it is possible to give each of the primary side and the secondary side a control power supply and a signal generation capability, it is not necessary to route the control signal, It is sufficient to extend only the power supply section, which has the effect of simplifying wiring and the like.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a basic configuration of the present invention.

FIG. 2 is a circuit diagram of the first embodiment of the present invention.

FIG. 3 is a circuit diagram of a main part of a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a main part of a third embodiment of the present invention.

FIG. 5 is a circuit diagram of a main part of a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram of a fifth embodiment of the present invention.

FIG. 7 is a circuit diagram showing a configuration of an invention of claim 4;

FIG. 8 is a circuit diagram of an embodiment of the invention of claim 4;

FIG. 9 is a circuit diagram showing a main configuration of the invention of claim 5;

FIG. 10 is a circuit diagram of an embodiment of the invention of claim 5;

FIG. 11 is a circuit diagram of the first embodiment of the invention of claim 6;

FIG. 12 is a circuit diagram of a second embodiment of the invention of claim 6;

FIG. 13 is an operation waveform chart of the second embodiment of the invention of claim 6;

FIG. 14 is a circuit diagram showing an example of a delay circuit according to a second embodiment of the invention of claim 6;

FIG. 15 is a circuit diagram showing another example of the delay circuit according to the second exemplary embodiment of the present invention.

FIG. 16 is a circuit diagram of a conventional example.

FIG. 17 is a circuit diagram of another conventional example.

[Explanation of Codes] 1 DC power supply 2 High frequency conversion circuit 3 Load 4 Low frequency conversion circuit 5 Current limiting circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Kambara 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (6)

[Claims] 1. A DC power supply, a high-frequency conversion circuit that converts the voltage of the DC power supply into a high-frequency rectangular wave voltage, a transformer that converts the output of the high-frequency conversion circuit into a voltage, and a rectifier circuit that rectifies the output of the transformer. In a load control device including an inverter circuit connected to the output of the rectifier circuit and a load connected to the output of the inverter circuit, a current limiting element for limiting the current of the load is connected between the transformer and the rectifier circuit. Load control device characterized by. 2. The load control device according to claim 1, wherein the load is a discharge lamp. 3. The load control device according to claim 1, wherein the transformer is a step-up type transformer in which the number of turns of the secondary winding is larger than that of the primary winding. 4. A DC power supply, a high frequency conversion circuit for converting the voltage of the DC power supply into a high frequency, a transformer for converting the output of the high frequency conversion circuit into a voltage, a rectification circuit for rectifying the output of the transformer, and an output of the rectification circuit. In a load control device comprising a low frequency conversion circuit for converting a low frequency into a low frequency and a load connected to an output of the low frequency conversion circuit, the control power source of the high frequency conversion circuit is supplied from the DC power source, and the low frequency conversion circuit is provided. A load control device characterized in that the control power supply of the circuit is configured to be supplied from the secondary side of the transformer. 5. A serial circuit of an inductor and a first capacitor, and a second capacitor having a smaller capacity than that of the first capacitor are connected in parallel to an input section of the high frequency conversion circuit. The load control device according to claim 4. 6. A high-frequency signal obtained from the control circuit of the high-frequency conversion circuit and a low-frequency signal obtained by frequency-dividing the high-frequency signal into a low-frequency signal are ANDed to obtain a control signal from the primary side of the transformer. A high-frequency pulse transformer for transmitting to the next side is provided, and the switching element of the low-frequency conversion circuit is driven by a drive signal obtained by rectifying and smoothing an output voltage of the high-frequency pulse transformer. The load control device according to claim 4.