KR200239224Y1 - Switched mode power supply apparatus - Google Patents

Abstract

The present invention discloses a switch mode power supply. The device generates high voltage by switching and transforming the DC voltage which is enabled and input in response to the first control signal in the start-up and active mode in response to the pulse width modulation signal, and the pulse width modulation by sensing the output current. A buck converter for varying the pulse width of the signal, detecting the state of the pulse width modulated signal and generating a protection signal, and is enabled in response to the second control signal in the start-up mode, and applies a high voltage in response to the first pulse drive signal. The lamp is started by converting and applying the AC voltage, and in the active mode, the lamp is turned on by applying the high voltage to the AC voltage in response to the second pulse driving signal having a lower frequency than the first pulse driving signal. A mechanism for generating the first pulse drive signal and the second pulse drive signal in response to the third control signal in the lighting circuit, the start-up and the active modes. A protection circuit for disabling the operation of the driving circuit in response to the circuit, the protection signal and the fourth control signal, and generating first, second and third control signals in the start-up and active modes, and detecting the level of the high voltage. And a control unit for generating the fourth control signal. Therefore, it is possible to extend the life of the lamp by starting the lamp for the projection display device and keeping the lighting stable.

Description

Switched mode power supply apparatus

The present invention relates to a switch mode power supply, and more particularly to a switch mode power supply for supplying a stable voltage to the metal halide lamp used as a light source of the projection display device.

Currently, metal halide lamps are widely used as light sources of projection display devices. This is because metal halide lamps have the highest light efficiency and color characteristics suitable for screen realization.

The metal halide lamp used in the projection display device must be started as a short ARC metal halide lamp, and accurate control must be made to keep the lighting stable to ensure the life of the lamp.

Therefore, the configuration of the switch mode power supply of the metal halide lamp used in the projection display device is complicated compared with the configuration of the switch mode power supply of the metal halide lamp for general lighting.

In particular, since a circuit for generating a pulse width modulated signal for controlling a switching transistor of a buck converter constituting a switch mode power supply of a conventional projection display device is composed of a plurality of timer circuits, There was a problem that the configuration is complicated.

It is an object of the present invention to provide a switch mode power supply that can simplify the circuit configuration, start a lamp for a projection display device, and keep the lighting stable.

A switch mode power supply for achieving this purpose generates a high voltage by switching and transforming a DC voltage that is enabled and input in response to a first control signal in start-up and active modes in response to a pulse width modulation signal. A buck converter for varying the pulse width of the pulse width modulated signal by sensing an output current and generating a protection signal by detecting a state of the pulse width modulated signal, in response to a second control signal in the start mode A lamp is started by converting and applying the high voltage to an AC voltage in response to the first pulse driving signal, and responding to the second pulse driving signal having a lower frequency than the first pulse driving signal in the active mode. Lighting means for lighting the lamp by converting and applying the high voltage to an AC voltage Disabling the driving means for generating the first pulse driving signal and the second pulse driving signal in response to the third control signal and the operation of the driving means in response to the protection signal and the fourth control signal. And protection means for generating the first, second and third control signals in the start-up and active modes, and generating the fourth control signal by detecting the level of the high voltage. It is done.

1 shows a configuration of a switch mode power supply of the present invention.

Hereinafter, the switch mode power supply of the present invention with reference to the accompanying drawings as follows.

Figure 1 shows the configuration of the switch mode power supply of the present invention, the linear filter 10, the power supply circuit 12, the output current adjusting circuit 14, the control means 16, the drive circuit 18, The protection circuit 20, the buck converter 22, the voltage distribution circuit 24, the start-up on / off switch 26, the lighting circuit 28, and the lamp 30 are comprised. The buck converter 22 is composed of a pulse width adjusting circuit 32, a switching transistor ST1, a diode D1, a resistor R1, an inductor L1, and a resistor C1. The voltage divider circuit 24 is composed of resistors R2 and R3. The start on / off switch 26 is constituted by a triac TR. The lighting circuit 28 includes switching transistors ST2 to ST5, a switch SW, an inductor L2, a voltage multiplication circuit 34, transformers TRS1 and TRS2, an arrester 36, and capacitors. It consists of (C4, C5, C6). The voltage multiplier circuit 34 is composed of diodes D2 and D3, resistors R4 and R5, and capacitors C2 and C3.

The function of the circuit shown in Fig. 1 is as follows.

The linear filter 10 removes noise of the supplied DC voltage. The voltage generation circuit 12 inputs the supplied DC voltage to generate voltages for the pulse width adjustment circuit 32, the control means 16, the drive circuit 18, and the protection circuit 20. The output current adjusting circuit 14 adjusts the current flowing through the lamp 30 in response to the control signal CON. The pulse width adjusting circuit 32 is enabled in response to the control signal c1 applied from the control means 16 and inputs the voltage of the node A to adjust the pulse width of the output signal PWM, and for a predetermined time. The output signal PWM is not generated during the operation or the protection output signal PRO is generated when the output signal PWM is kept on. That is, the pulse width of the output signal PWM is varied according to the change of the voltage of the node A. If the voltage of the node A is lowered, the pulse width of the output signal PWM is increased, and if the voltage of the node A is increased, the pulse width of the output signal PWM is reduced. The switching transistor ST1 is turned on in response to the output signal PWM to transmit the output voltage of the linear filter 10 to the node B. The inductor L transforms the voltage of the node B to generate a lamp power supply voltage. Capacitor C1 smoothes the voltage generated from inductor L. The diode D1 and the resistor R1 flow a current flowing through the inductor L and the capacitor C1 when the switching transistor ST1 is turned off. The resistor R1 senses the current flowing through the lamp 30. The voltage divider circuit 24 divides the voltage by the resistors R2 and R3 to generate the divided voltage VD. The triac TR is turned on in response to the control signal c4. The control means 16 generates the control signals c1 to c4 and the comparison voltage COM in response to the on / off signal, and inputs the voltage VD to input the voltage VD so that the control signal (or c2). The driving circuit 18 is turned on in response to the control signal c3 to generate the driving signals S1, S2, S3, and S4, and turned off in response to the signal P. The control signal c3 generated at this time is a pulse signal and is generated at a high frequency in the start mode and at a low frequency in the active mode. The protection circuit 20 compares the voltage of the protection signal PRO with the comparison voltage COM, and when the voltage of the protection signal PRO is greater than the comparison voltage COM and the protection control signal c2 is generated, the driving circuit 18. Generates a signal P for turning off. The switch SW is turned on in the start-up mode and turned off in the active mode in response to the output signal of the triac TR. The switching transistors ST2 to ST5 alternately turn on the DC voltage by turning on the switching transistors ST2 and ST5 and the switching transistors ST3 and ST4 in response to the driving signals S1, S2, S3, and S4. It will be changed to AC voltage. The voltage multiplication circuit 34 doubles the voltage applied by the operation of the switching transistors ST2, ST3, ST4, and ST5 in the start-up mode and applies the voltage to the arrester 36. The arrester 36 generates a spark voltage when a voltage doubled by the voltage multiplication circuit 34 is applied in the start-up mode. When the spark voltage is generated by the arrester 36 in the start-up mode, the transformers TRS1 and TRS2 flow current to the primary side, and this current is induced to the secondary side to light the lamp 30, and in the active mode. The current applied through the switching transistors ST2, ST3, ST4, and ST5 flows to the secondary side to light the lamp 30. Capacitors C4 and C5 connected to the secondary side of transformers TRS1 and TRS2 are for third harmonic tuning.

The operation of the circuit shown in FIG. 1 is divided into a standby mode, a startup mode, and an active mode as follows.

When the DC voltage is applied in the standby mode and the on / off signal is in the off state, the voltage generating circuit 12 causes the pulse width adjusting circuit 32, the control means 16, the driving circuit 18, and the protection circuit ( Voltage is applied.

When the DC voltage is applied in the start-up mode and the on / off signal is switched to the on state, the control means 16 generates the control signals C1, C3, C4 to generate the pulse width adjusting circuit 32 and the driving circuit. Enable the operation of 18, and turn on the triac TR. At this time, the control signal c3 generated from the control means 16 is a high frequency pulse signal for resonating the secondary coils and the capacitors C4 and C5 of the transformers TRS1 and TRS2 at three harmonics. The pulse width adjusting circuit 32 is enabled in response to the control signal c1 to input the voltage and the comparison voltage of the node A to generate the output signal PWM, and the output signal PWM occurs for a predetermined time. If not, or occurs for a predetermined time or more, the protection control signal PRO is generated. The switching transistor ST1 is turned on when the output signal PWM is generated to transmit the output voltage of the linear filter 10 to the node B. The inductor 22 transforms the voltage of the node B to generate a voltage of about 150V. When the triac TR is turned on, the switch SW is turned on to apply a voltage of about 150V to the lighting circuit 28. The driving circuit 18 alternately generates the driving signals S1 and S4 and the driving signals S2 and S3 in response to the control signal c3. Accordingly, the switching transistors ST3 and ST4 and the switching transistors ST2 and ST5 are alternately turned on to convert the DC voltage into an AC voltage. When the switching transistors ST3 and ST4 are turned on, a voltage of about 150V is doubled through the diode D2, the resistor R4, and the capacitor C3, and when the switching transistors ST2 and ST5 are turned on, A voltage of about 150V is doubled through the capacitor C2, the resistor R5, and the diode D3. The arrester 36 generates the spark voltage by the voltage doubled. As a result, current flows in the primary coils of the transformers TRS1 and TRS2, and the current is induced to the secondary coil. At this time, the coils on the secondary side of the transformers TRS1 and TRS2 and the capacitors C4 and C5 cause three harmonic resonances to generate a high voltage. This high voltage breaks the insulation of the lamp 30 and causes a large amount of current to flow rapidly, thereby lighting the lamp 30. When the protection control signal PRO is generated from the pulse width adjustment circuit 32, the protection circuit 20 compares the control voltage COM generated from the control means 16 with the protection control signal PRO to drive circuit 18. The lamp 30 is protected by generating a signal P for turning off) or by turning off the driving circuit 18 in response to the control signal c2.

When the lamp 30 is turned on in the start-up mode, the control means 16 switches from the start mode to the active mode to control the operation of the device.

When switching to the active mode, the control means 16 turns off the triac TR by the control signal c4, lowers the frequency of the control signal c3 applied to the driving circuit 18, and compares the voltage COM. The level of is converted and the detection level of the voltage VD is converted. The reason for converting the level of the comparison voltage COM and the detection level of the voltage VD is that the level of the voltage output through the inductor L1 in the start-up mode and the voltage output through the inductor L1 in the active mode Since the levels are different, the protection circuit 20 is operated by converting the level of the comparison voltage COM and the detection level of the voltage VD. When the triac TR is turned off, the switch SW is turned off so that the voltage multiplier circuit 34 and the arrestor 36 do not operate, and the frequency of the control signal c2 is lowered so that the driving circuit ( The frequencies of the driving signals S1, S2, S3, and S4 output from 18 become low. The resistor R1 senses the current flowing through the lamp 30, and the pulse width adjusting circuit 32 senses the voltage of the node A to adjust the pulse width of the output signal PWM. When a large amount of current flows into the lamp 30 in the start-up mode, this current is sensed by the resistor R1, and the pulse width adjusting circuit 32 adjusts the pulse width of the output signal PWM to switch the transistor ST1. Will lower the output voltage. As a result, the output voltage of the inductor L1 drops to about 20V. This voltage is applied to the lamp 30 through the secondary side coils of the transformers TRS1 and TRS2 by the operation of the switching transistors ST2, ST3, ST4, ST5. Initially, a voltage of about 20V is applied to the lamp 30 to reduce the current flowing through the lamp 30. When this current is detected by the resistor R1, the pulse width adjusting circuit 32 inputs the voltage of the node A to increase the voltage of the node B by increasing the pulse width of the output signal PWM. The inductor L1 transforms the voltage of the node B and outputs it. By repeatedly performing such an operation, the output voltage of the inductor L1 is increased to about 80V. When the output voltage of the inductor L1 rises to about 80V, a stable voltage has been reached. Therefore, the operation to maintain the voltage is performed. When the protection control signal PRO is generated from the pulse width adjusting circuit 32, the protection circuit 20 compares the control voltage COM with the protection control signal PRO to turn off the driving circuit 18. ) Or protect the lamp 30 by turning off the driving circuit 18 in response to the control signal c2.

In particular, the switch mode power supply of the present invention shown in Fig. 1 uses the pulse width adjusting circuit 32 constituting the buck converter in particular using one IC, for example, KA555, a timer IC manufactured by Fairchild. By configuring, the circuit configuration is simplified.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art various modifications and variations of the present invention without departing from the spirit and scope of the present invention described in the claims below I can understand that you can.

Therefore, the switch mode power supply of the present invention has a simple circuit configuration and can stably start and light a lamp for a projection display device.

Claims (3)

A high voltage is generated by switching and transforming a DC voltage that is enabled and input in response to the first control signal in the start-up and active modes in response to a pulse width modulation signal, and detects an output current of the pulse width modulation signal. A buck converter for varying a pulse width and detecting a state of the pulse width modulated signal to generate a protection signal; It is enabled in response to a second control signal in the start mode and starts a lamp by converting and applying the high voltage to an AC voltage in response to a first pulse drive signal, and in the active mode the first pulse drive signal. Lighting means for lighting the lamp by converting and applying the high voltage into an AC voltage in response to a second pulse drive signal having a lower frequency; Driving means for generating the first pulse driving signal and the second pulse driving signal in response to a third control signal in the start-up and active modes; Protection means for disabling operation of the driving means in response to the protection signal and a fourth control signal; And And a control means for generating the first, second and third control signals in the start-up and active modes and for generating the fourth control signal by detecting the level of the high voltage. Feeding device. The method of claim 1, wherein the buck converter A switching transistor for transferring the DC voltage in response to the pulse width modulation signal; An inductor and a capacitor connected in series between an output terminal of the switching transistor and a ground voltage and transforming the DC voltage to generate the high voltage; A diode connected between an output terminal of the switching transistor and an output current detection node to flow a current flowing through the inductor and the capacitor when the switching transistor is turned off; An output current detection resistor connected between the output current detection node and a ground voltage and detecting an output current flowing through the lamp and flowing a current flowing through the inductor and the capacitor when the switching transistor is turned off; And And a pulse width adjusting means for generating the protection signal by varying a pulse width of the pulse width modulation signal in response to a voltage of the output current detection node, and detecting a state of the pulse width modulation signal. Switch mode power supply. The method of claim 2, wherein the pulse width adjusting means Switch mode power supply, characterized in that implemented in one integrated circuit.