JP2007207708A - Discharge lamp lighting circuit with life protection circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting circuit capable of detecting capacitance drop of an electrolytic capacitor and thereafter never carrying a current to the discharge lamp lighting device. <P>SOLUTION: A microcomputer 10 inputs, from an input terminal 13, a voltage of the electrolytic capacitor 6 converted in level by a voltage conversion circuit 9, determines its pattern, determines that the capacitance of the electrolytic capacitor 6 drops when the pattern coincides with a determination criterion, and outputs a signal for forcibly turning on a switching element 12 to a switching element driving circuit 11 from an output terminal 14. The switching element driving circuit 11 turns on the switching element 12 in response to the signal from the microcomputer 10. As a result, an overcurrent is generated in the direction shown by an arrow 15, an overcurrent protection element 2 is melted down, and this discharge lamp lighting circuit 100 is disconnected from a power source 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting circuit according to the premise of claim 1.

  In recent years, heat insulation measures have been taken in residential houses, and the heat generated by the heating equipment and the heat generated by the lighting fixtures themselves are easily trapped by laying the heat insulating material behind the ceiling, and the temperature environment in which the lighting fixtures are installed is increasing. Depending on the consumer's usage conditions, it may be used in a temperature environment that exceeds the manufacturer's expectations, and the temperature of each part of the discharge lamp lighting circuit exceeds the design value, and the electrolytic capacitor that stores the energy given to the discharge lamp is also thermally There is an increasing number of cases where stress increases and the safety valve of the electrolytic capacitor opens. The phenomenon at that time is that the electrolytic solution of the electrolytic capacitor is vaporized and vapor is generated. However, it is easy for general consumers to misunderstand it as smoke. There was a need to prevent the valve. In addition, even if it is not mistaken for smoke, the electrolytic capacitor maker says that the steam or the electrolyte that has returned to the liquid after it has cooled has no effect on the human body, but the general consumer has the image that it is bad for the human body. It is also to avoid being held.

  The life of the discharge lamp lighting circuit is mainly governed by a decrease in the capacitance of the electrolytic capacitor, which is one of the components, that is, the life of the electrolytic capacitor. Conventionally, when the end of the electrolytic capacitor life in the circuit is reached, the electrolytic solution filled may be ejected to the outside of the component by opening the safety valve of the electrolytic capacitor. It is said that at the end of the life of the electrolytic capacitor, the capacity decrease is accelerated.

In Patent Document 1, such a situation is unavoidable because the discharge lamp lighting device is permanently stopped only when the discharge lamp does not light normally due to an abnormality in the discharge lamp, parts, or the like.
JP-A-7-263150

  An object of the present invention is to provide a discharge lamp lighting circuit that detects a decrease in the capacitance of an electrolytic capacitor and does not energize the discharge lamp lighting circuit thereafter.

The discharge lamp lighting circuit of the present invention includes a switching element driving circuit for driving a switching element,
An overcurrent protection element that is connected in series between the switching element and the AC power supply terminal and blows when an overcurrent flows, a voltage conversion circuit that converts the output voltage of the electrolytic capacitor, and an output voltage of the voltage conversion circuit are input. And a control circuit for determining a pattern of the output voltage and outputting a signal for forcibly turning on the switching element to the switching element drive circuit when it is determined that the capacitance of the electrolytic capacitor has decreased. The voltage conversion circuit converts the output voltage of the electrolytic capacitor to a voltage level suitable for the input signal of the control circuit.
When a decrease in the capacitance of the electrolytic capacitor that stores energy applied to the discharge lamp is detected, an overcurrent is generated, the overcurrent protection element is blown, and the discharge lamp lighting circuit is disconnected from the AC power source.

  The discharge lamp lighting circuit cannot be used before the electrolytic capacitor is discharged and the electrolytic solution is ejected when the safety valve is opened. Therefore, the interior of the lighting fixture and the surroundings of the lighting fixture can be avoided. In addition, it is highly likely that the jet of electrolyte is mistaken for smoke by general consumers, and there is a strong tendency to have a dangerous impression, but there is no fear of giving them negative images.

  Also, in the method of stopping the current to the electrolytic capacitor by stopping the operation of the power factor correction circuit, for example, by stopping the operation of the power factor correction circuit, the current is supplied to the electrolytic capacitor until the protection is activated when the power is turned on. Especially when the power is turned on, the operating conditions are severe, such as high voltage and current. In the unlikely event that the user repeatedly turns on / off the power supply, the safety valve of the electrolytic capacitor may open. Since the overcurrent protection element is forcibly blown out, it is possible to prevent stress destruction to the circuit components due to repeated operations by the user to turn on the power. In addition, stress applied to other parts due to the end of life of the electrolytic capacitor can be prevented, and secondary problems can be prevented.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram of a discharge lamp lighting circuit according to an embodiment of the present invention.

  The discharge lamp lighting circuit 100 includes an overcurrent protection element 2, a filter circuit 3, a rectifier circuit 4, a power factor correction circuit 5, an electrolytic capacitor 6, a discharge lamp drive circuit 7, a voltage conversion circuit 9, a microcomputer 10, and a switching element drive circuit 11. Switching element 12.

  The overcurrent protection element 2 protects the power supply 1 and the circuit 100 when an overcurrent flows in the circuit 100. The filter circuit 3 is for EMI (Electromagnetic Interference) countermeasures. The rectifier circuit 4 performs full-wave rectification of the AC power supply. The power factor improving circuit 5 inputs the full-wave rectified AC power source by the rectifying circuit 4 and improves the power factor by a control element 5e described later. The switching element 12 performs a switching operation in the power factor correction circuit 5. The electrolytic capacitor 6 stores energy to be given to the discharge lamp 8 in advance. The discharge lamp drive circuit 7 drives the discharge lamp 8 based on the energy stored in the electrolytic capacitor 6. The voltage conversion circuit 9 converts the voltage of the electrolytic capacitor 6 to a voltage level suitable for the input signal of the microcomputer 10. The switching element drive circuit 11 is controlled by the microcomputer 10 to control the switching element 12.

  The microcomputer 10 inputs the voltage of the electrolytic capacitor 6 that has been level-converted by the voltage conversion circuit 9 from the input terminal 13, determines the pattern, and if it matches the determination criteria, the capacitance of the electrolytic capacitor 6 decreases. And a signal for forcibly turning on the switching element 12 is output from the output terminal 14 to the switching element drive circuit 11. Here, when the voltage waveform of the input terminal 13 becomes higher than the reference value for a certain period of time, for example, 5 seconds or more, it is determined that the determination criterion is met. Here, the term “fixed time” is used to distinguish from a case where an instantaneously larger value than the reference value may occur frequently. The switching element drive circuit 11 turns on the switching element 12 in response to a signal from the microcomputer 10. As a result, an overcurrent is generated in the direction indicated by the arrow 15, the overcurrent protection element 2 is melted, and the discharge lamp lighting circuit 100 is disconnected from the power source 1.

  FIG. 2 shows an example of the voltage waveform of each part of the discharge lamp lighting circuit 100 of FIG. At time t1, the input voltage of the input terminal 13 of the microcomputer 10 exceeds the voltage threshold value 3.5V, and this state continues for a certain time until time t2. During this time, a voltage that alternately repeats 0 V and 12 V is applied between the gate and source terminals of the switching element 12. At time t2, as described above, a signal for forcibly turning on the switching element 12 is output from the microcomputer 10 to the switching element drive circuit 11, and a voltage of 12 V is continuously applied between the gate and source terminals of the switching element 12. On the other hand, the voltage between the drain and source terminals of the switching element 12 is approximately 0V. As a result, an overcurrent flows through the overcurrent protection element 2, the overcurrent protection element 2 is melted, and the discharge lamp lighting circuit 100 is disconnected from the power source 1.

  FIG. 3 is a circuit diagram of a first specific example of the discharge lamp lighting circuit 100.

  The overvoltage protection element 16 serves to protect the circuit 100 when an overvoltage is input to the circuit 100. The filter circuit 3 includes capacitors 3a and 3c and a coil 3b. The filter circuit 3 includes diodes 4a, 4b, 4c, and 4d. The power factor correction circuit 5 includes capacitors 5a and 5d, resistors 5b, 5c, 5f, 5h, 5k, 5l, 5n, and 5o, a control element 5e that is a general-purpose power factor improvement control IC, and a coil 5g. , Diodes 5i and 5m, an electrolytic capacitor 5j, and a switching element 12 that performs a switching operation. The voltage conversion circuit 9 includes resistors 9a, 9b and 9d, a diode 9c, and a capacitor 9e. The discharge lamp driving circuit 7 includes FET transistors 7b and 7d as switching elements, resistors 7a and 7c, a driving element 7h for driving the FET transistors 7b and 7d, a coil 7e, and capacitors 7f and 7g. The microcomputer 10 has a function of giving an oscillation timing signal to the driving element 7h in addition to the function described with reference to FIG. The switching element drive circuit 11 includes a transistor 11c and resistors 11a, 11b, and 11d.

  Next, the operation of this example will be described.

  The AC input passes through the filter circuit 3 and is full-wave rectified by the rectifier circuit 4 and input to the power factor correction circuit 5. The power factor correction circuit 5 performs switching control of the switching element 12 by the control element 5e. An electrolytic capacitor 6 is connected to the output of the power factor correction circuit 5, and the electrolytic capacitor 6 stores energy. The half-bridge circuit driving element 7h alternately switches the switching elements 7b and 7d of the half-bridge circuit by the timing signal output from the microcomputer 10, and the energy of the electrolytic capacitor 6 is input to the discharge lamp driving circuit 7 and the coil 7e. Then, an AC voltage is generated at the output terminal 17 using the resonance action of the capacitors 7f and 7g, and the discharge lamp 8 is turned on.

  At this time, when the capacitance of the electrolytic capacitor 6 decreases, the amplitude of the ripple voltage of the electrolytic capacitor 6 increases, and the peak voltage becomes higher than when the capacitance of the electrolytic capacitor 7 hardly decreases. This voltage is input from the input terminal 13 to the microcomputer 10 via the voltage conversion circuit 9. When the signal voltage exceeds a certain value for a certain time, the microcomputer 10 determines that the capacitance of the electrolytic capacitor 6 is lowered, and the switching element 12 is forced to be turned on from the output terminal 14 to the switching element drive circuit 11. Output a signal. The switching element 12 is turned on regardless of the control of the control element 5e, an overcurrent flows through the circuit 100, the overcurrent protection element 2 is melted, and the discharge lamp lighting circuit 100 is disconnected from the AC power source 1.

  FIG. 4 is a circuit diagram of a second specific example of the discharge lamp lighting circuit 100.

  In this specific example, the voltage conversion circuit 9 for converting the voltage of the control element 5e in the first specific example into a voltage range suitable for the input signal of the microcomputer 10 for monitoring the voltage of the electrolytic capacitor 6 is provided in the microcomputer 10. Are also used as elements (resistors 5n, 5o) in the power factor correction circuit 5. The switching element drive circuit 11 includes transistors 11c and 11e and resistors 11a and 11b.

  A signal of an input voltage element (5b, 5c) provided for monitoring a voltage waveform input to the power factor correction circuit 5 is input from the input terminal 18 to the microcomputer 10. A signal of a voltage conversion circuit for converting the voltage range suitable for the input signal of the microcomputer 10 for monitoring the voltage of the electrolytic capacitor 6 is input to the microcomputer 10 from the input terminal 13. These two input signals are synchronized as shown in FIG. 4, and the microcomputer 10 reads the signal at the input terminal 13 at the peak timing of the signal input to the input terminal 18 and exceeds the judgment value over a certain cycle. Then, it is determined that the capacity of the electrolytic capacitor 6 is reduced, and a signal is output from the output terminal 14 to the switching element drive circuit 11 to forcibly turn on the switching element 12. As a result, the switching element 12 is turned on, an overcurrent flows through the circuit 100, the overcurrent protection element 2 is melted, and the discharge lamp lighting circuit 100 is disconnected from the AC power source 1.

It is a block diagram of the discharge lamp lighting circuit by one Embodiment of this invention. It is a figure which shows the example of the voltage waveform of each part of the discharge lamp lighting circuit 100 of FIG. 1 is a circuit diagram of a first specific example of a discharge lamp lighting circuit 100. FIG. 3 is a circuit diagram of a second specific example of the discharge lamp lighting circuit 100. FIG. 6 is a waveform diagram of input / output voltages of a power factor correction circuit 5. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Overcurrent protection element 3 Filter circuit 3a, 3c Capacitor 3b Coil 4 Rectifier circuit 4a-4d Diode 5 Power factor improvement circuit 5a, 5d Capacitor 5b, 5c, 5f, 5h, 5k, 5l, 5n, 5o Resistance 5e Control element (Power factor correction IC)
5g Coil 5i, 5m Diode 5j Electrolytic capacitor 6 Electrolytic capacitor 7 Discharge lamp drive circuit 7a, 7c Resistor 7b, 7d FET transistor 7e Coil 7f, 7g Capacitor 7h Drive element 8 Discharge lamp 9 Voltage conversion circuit 9a, 9b, 9d Resistor 9c Diode 9e capacitor 10 microcomputer 11 switching element drive circuit 11a, 11b resistor 11c, 11d transistor 12 switching element 13 input terminal 14 output terminal 15 current loop when switching element is forced on 16 overvoltage protection element 17 output terminal 18 input terminal 100 discharge lamp lighting circuit

Claims (4)

It has a rectifier circuit that rectifies the AC power supply voltage and a switching element that performs a switching operation. The output voltage of the rectifier circuit is input, and the switching element is controlled in accordance with the phase of the output voltage to improve the power factor. A power factor improving circuit for performing the above, an electrolytic capacitor connected to the output of the power factor improving circuit for preliminarily storing energy applied to the discharge lamp, and a discharge lamp driving for driving the discharge lamp based on the energy stored in the electrolytic capacitor In a discharge lamp lighting circuit equipped with a circuit,
A switching element driving circuit for driving the switching element;
An overcurrent protection element connected in series between the switching element and the AC power supply terminal and fusing when an overcurrent flows;
A voltage conversion circuit for converting the output voltage of the electrolytic capacitor;
The output voltage of the voltage conversion circuit is input, the pattern of the output voltage is determined, and when it is determined that the capacitance of the electrolytic capacitor has decreased, a signal for forcibly turning on the switching element is switched to the switching circuit. A control circuit for outputting to an element drive circuit, wherein the voltage conversion circuit converts the output voltage of the electrolytic capacitor to a voltage level suitable for an input signal of the control circuit,
A discharge lamp lighting circuit with a life protection circuit.   The discharge lamp lighting circuit according to claim 1, wherein the control circuit is a microcomputer.   2. The discharge lamp according to claim 1, wherein the control circuit determines that the capacitance of the electrolytic capacitor has decreased when an output voltage of the voltage conversion circuit becomes higher than a predetermined reference value for a predetermined time or more. Lighting circuit.   2. The discharge lamp lighting circuit according to claim 1, wherein the control circuit inputs a monitoring signal of the input voltage from the power factor correction circuit, and reads the output voltage of the voltage conversion circuit at the peak timing.

Images