JP2008154379A - Step-up chopper regulator circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a step-up chopper regulator circuit wherein the convenience of equipment is not impaired and a trouble of current leakage can be prevented as much as possible even when any anomaly occurs in the circuit. <P>SOLUTION: The regulator circuit includes a coil with a power supply connected to the preceding stage; an output diode connected to the stage subsequent to the coil and having rectifying action from the preceding stage side to the subsequent stage side; an output terminal, provided in the stage subsequent to the diode, to which a predetermined load is connected; and switching elements, provided in the grounding path connecting the joint between the coil and the diode and a ground point, for switching the grounding path between conduction and non-conduction. The regulator circuit includes: a detecting means for detecting whether or not the current or the like in the circuit exceeds a predetermined threshold value; and a switch that is provided in a path connecting the power supply and the load and makes it possible to connect and disconnect the preceding stage side and the subsequent stage side of the path. The switching of the switch is carried out according to the result of detection by the detecting means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a step-up chopper regulator circuit that supplies power to an electrical load such as an LED.

  Conventionally, for example, a boost chopper regulator is often used as a power supply circuit for driving an LED. Here, an LED driver shown in FIG. 10 will be described as an example of a conventional boost chopper regulator circuit.

  The LED driver shown in this figure includes a DC power supply 11, an input capacitor 12, a coil 13, an output diode 14, an output capacitor 15, a resistance element R1, a chopper regulator IC 20, and the like. The chopper regulator IC includes switching transistors (21a, 21b), an amplifier 24, an oscillation circuit 25, a drive circuit 26, a PWM comparator 28, an error amplifier 29, a reference voltage source 30, and the like.

  When driving the LED group 50 (one LED or a plurality of LEDs connected in series) as a load in such a configuration, the current flowing in the LED group 50 and the voltage (feedback) generated by the resistance element R1. Voltage) and the reference voltage from the reference voltage source 30 are error-amplified by the error amplifier 29. The output of the error amplifier 29 and the output of the amplifier 24 are subjected to pulse width modulation by the PWM comparator 28, and the switching transistors (21a, 21b) are controlled via the drive circuit 26 by this signal.

  When the switching transistors (21a, 21b) are ON, the current flows to the coil 13 and the switching transistors (21a, 21b), whereby energy is stored in the coil 13, and during this period, the LED capacitor is connected from the output capacitor 15 to the LED group. 50 is supplied with current. On the other hand, when the switching transistors (21a, 21b) are OFF, the input voltage is boosted by the energy stored in the coil 13 to charge the output capacitor 15 and supply current to the LED group 50.

As a safety device, an overvoltage protection circuit 31, an overcurrent protection circuit 27, an overheat protection circuit 32, and the like are provided. When an abnormality occurs, power supply is stopped through the drive circuit 26. . In this way, even when an abnormality occurs in the circuit for some reason, an attempt is made to avoid damage to the circuit as much as possible.
JP-A-5-199740 JP-A-8-31673

  As described above, in the step-up chopper regulator circuit, consideration is given to appropriately controlling the drive circuit when an abnormality occurs. However, for example, when a part of the circuit such as the output terminal is short-circuited to the ground point, there is still a possibility that current leaks from here. This is a big problem in securing the safety of the device.

  In order to cope with such a problem, as shown in FIG. 10, it may be possible to provide a fuse 16 in a part of the power supply path. According to this, it is possible to prevent a situation in which current leaks to the subsequent stage by cutting off the power supply path itself at the time of abnormality.

  However, when a fuse is provided in this way, it may be necessary to replace it when the fuse is blown, or a new problem such as a blown fuse due to the occurrence of an inrush current may occur, which may impair the convenience of the device. is there. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a boost chopper regulator circuit capable of preventing a current leakage as much as possible even when an abnormality occurs in the circuit without impairing the convenience of the device.

  In order to achieve the above object, a step-up chopper regulator circuit according to the present invention includes a coil connected to a power source in a previous stage, a rectifier element connected to a subsequent stage of the coil and having a rectifying action from the front stage side to the rear stage side. , Provided on the ground path connecting the output terminal provided at the subsequent stage of the rectifier element to which a predetermined load is connected and the intermediate point of the coil and the rectifier element and the ground point, and conduction / non-conduction of the ground path A step-up chopper regulator circuit in which power output to the load is controlled through the switching, and any of current, voltage, and temperature in the circuit is a predetermined threshold value. Detecting means for determining whether or not the power supply is exceeded, and a path connecting the power source and the load, and connecting / disconnecting the front stage side and the rear stage side in the path Includes a switch that allows replacement, the switching of the switch is configured to be made in accordance with a detection result of said detecting means (first configuration).

  According to this configuration, it is possible to block the path connecting the power source and the load when an abnormality (a state where the current in the circuit or the like exceeds a predetermined threshold) is detected by the detection unit. For this reason, even when an abnormality occurs, it is possible to prevent a problem that current leaks out as much as possible.

  Further, since the switch can be switched between connection and non-connection, even after the path is shut off (non-connection state), it is easy to return to the normal state by setting the switch again to the connection state. Therefore, the process of replacing the fuse is unnecessary, and it is possible to avoid as much as possible that the convenience of the device is impaired.

  More specifically, as the first configuration, the switch may have a configuration (second configuration) provided between the rectifying element and the output terminal, and the switch includes the coil. It is good also as a structure (3rd structure) provided in the front | former stage side.

  Further, as the detecting means in any one of the first to third configurations, specifically, a configuration for detecting whether or not the current or voltage output to the load exceeds a predetermined threshold (fourth) Configuration), a configuration for detecting whether or not the current in the previous stage of the coil exceeds a predetermined threshold (fifth configuration), and whether or not the current in the ground path exceeds a predetermined threshold Configuration (sixth configuration), configuration for detecting whether the coil temperature exceeds a predetermined threshold (seventh configuration), whether the temperature of the rectifying element exceeds a predetermined threshold It is good also as a structure (8th structure) etc. which detect this. With such a configuration, it is possible to detect whether there is an abnormality in the circuit.

  Further, the voltage at the latter stage of the load is fed back, and the switching is controlled based on the voltage, the chopper regulator circuit according to any one of the first to third configurations, wherein the detection unit includes the detection unit A configuration for detecting whether or not the voltage to be fed back exceeds a predetermined threshold value (a ninth configuration) may be employed. With such a configuration, it is possible to detect whether there is an abnormality in the circuit.

  The step-up chopper regulator circuit according to the present invention is provided in a coil connected to a power source in the previous stage, an FET connected to the subsequent stage of the coil and having a rectifying action from the previous stage side to the subsequent stage side, and in the subsequent stage of the FET. An output terminal to which a predetermined load is connected, and a switching element provided on a ground path connecting the intermediate point of the coil and the FET and a ground point, and switching conduction / non-conduction of the ground path, In the step-up chopper regulator circuit in which the power output to the load is controlled through the switching and the synchronous rectification method using the FET is adopted, the current, voltage, and temperature of the circuit are increased. Detecting means for detecting whether any of them exceeds a predetermined threshold value, and depending on the detection result in the detecting means, Side is a structure in which and a blocking means for controlling the FET so that the non-conductive (Configuration 10).

  According to this configuration, since the synchronous rectification method is employed, the efficiency of power supply can be further improved. Since the FET used for the synchronous rectification operation is also used as a switch for switching the connection / disconnection of the path connecting the power supply and the load, the power supply path is interrupted in the event of an abnormality without providing a separate switch means. Can be realized.

  Further, in the tenth configuration, the detection means may be configured to detect whether or not the temperature of the FET exceeds a predetermined threshold (11th configuration). With such a configuration, it is possible to detect the presence or absence of an abnormality in the circuit by the detection means.

  The step-up chopper regulator circuit according to the present invention is a chopper regulator circuit that adjusts electric power obtained from a power source and supplies the electric power to a predetermined load, and any of current, voltage, and temperature in the circuit is predetermined. Detecting means for detecting whether or not a threshold value is exceeded, and a switch provided in a path connecting the power source and the load, and capable of switching connection / disconnection between the front stage side and the rear stage side in the path, The switch is switched according to the detection result of the detection means (a twelfth configuration).

  In addition, the boost chopper regulator circuit according to the present invention adjusts the electric power obtained from the power supply and supplies it to a predetermined load, and the boost chopper regulator circuit to which a synchronous rectification method using a rectifying FET is applied. In the circuit, a detecting means for detecting whether any one of a current, a voltage, and a temperature in the circuit exceeds a predetermined threshold value, and the front side and the rear side are not in accordance with a detection result in the detecting means. It is set as the structure (13th structure) provided with the interruption | blocking means which controls the said FET so that it may become conduction | electrical_connection.

  Moreover, if the electronic device has a configuration (fourteenth configuration) using the step-up chopper regulator according to any one of the first to thirteenth configurations, an electronic device that can enjoy the advantages according to the configuration is realized. It is possible.

  As described above, according to the step-up chopper regulator circuit of the present invention, when an abnormality (a state in which a current in the circuit exceeds a predetermined threshold) is detected by the detection means, the path connecting the power source and the load is blocked. It becomes possible. For this reason, even when an abnormality occurs, it is possible to prevent a problem that current leaks out as much as possible.

  Further, since the switch can be switched between connection and non-connection, even after the path is shut off (non-connection state), it is easy to return to the normal state by setting the switch again to the connection state. Therefore, the process of replacing the fuse is unnecessary, and it is possible to avoid as much as possible that the convenience of the device is impaired.

  Embodiments of the present invention will be described below with reference to Examples 1 to 6.

[Example 1]
As an embodiment 1 of the present invention, an LED driver including a boost chopper regulator circuit will be described. FIG. 1 shows a configuration diagram of the LED driver. As shown in this figure, the LED driver includes a DC power supply 11, an input capacitor 12, a coil 13, an output diode 14, an output capacitor 15, a resistor element R1, a switch 41, an output abnormality detection circuit 42, a chopper regulator IC 20, and the like. Yes. Thereby, electric power is supplied to the LED group 50.

  The negative terminal of the DC power supply 11 is grounded, while the positive terminal is connected to one end of the input capacitor 12 and one end of the coil 13. The other end side of the input capacitor 12 is grounded. The anode side of the diode 14 is connected to the other end of the coil 13, while the cathode side is connected to one end of the switch 41. Note that the switch 41 can switch connection / disconnection of both ends (upstream side and downstream side), and is normally connected.

  The other end of the switch 41 is connected to the upstream side of the output abnormality detection circuit 42. The downstream side of the output abnormality detection circuit 42 is grounded via the output capacitor 15. An output terminal is provided between the switch 41 and the output abnormality detection circuit 42, and the upstream side of the LED group 50 is connected to this output terminal to receive power supply. The downstream side of the LED group 50 is grounded via a resistor R1. The switching of the switch 41 is controlled by the output abnormality detection circuit 42 as will be described later.

  The chopper regulator IC 20 includes a switching transistor (21a, 21b), a resistance element R2, a comparator 23, an amplifier 24, an oscillation circuit 25, a drive circuit 26, an overcurrent protection circuit 27, a PWM comparator 28, an error amplifier 29, and a reference voltage. A source 30, an overvoltage protection circuit 31, an overheat protection circuit 32, an ON / OFF circuit 33, and the like are provided. Also, a terminal such as Vin is provided, and connection with an external device is possible.

  The switching transistor 21b is composed of an n-channel MOSFET, the drain is connected to the downstream side of the coil 13, and the source is grounded. The switching transistor 21b is composed of an n-channel MOSFET, the drain is connected to the downstream side of the coil 13, and the source is grounded via the resistance element R2. Note that the type of each switching transistor is not limited to these.

  The voltage generated by the resistance element R2 is detected by the comparator 23. This detection voltage is combined with a triangular wave output from the oscillation circuit 25 by the amplifier 24 and input to one input terminal of the PWM comparator 28. In the error amplifier 29, the voltage on the downstream side of the LED group 50 is input to one input terminal as a feedback voltage, and the reference voltage from the reference voltage source 30 is input to the other input terminal. The comparison result of both inputs is output to the other input terminal of the PWM comparator 28.

  The PWM comparator 28 compares the voltages input to both input terminals and outputs a signal corresponding to this to the drive circuit 26. The drive circuit 26 controls the switching transistors (21a, 21b) based on the signal input from the PWM comparator 28.

  With such a configuration, when the switching transistors (21a, 21b) are ON, the current flows to the coil 13 and the switching transistors (21a, 21b), whereby energy is stored in the coil 13, and in this period Current is supplied from the output capacitor 15 to the LED group 50. On the other hand, when the switching transistors (21a, 21b) are OFF, the input voltage is boosted by the energy stored in the coil 13 to charge the output capacitor 15 and supply current to the LED group 50.

  The overcurrent protection circuit 27 monitors the source current of the switching transistor 21a. When the current exceeds a predetermined threshold, the overcurrent protection circuit 27 considers that the current is abnormal and controls the drive circuit 26 so that the current value decreases. . The overvoltage protection circuit 31 monitors the voltage output to the LED group 50. When this voltage exceeds a predetermined threshold value, the overvoltage protection circuit 31 regards it as abnormal and controls the drive circuit 26 so that the voltage value decreases.

  The overheat protection circuit 32 includes a temperature sensor that detects the temperature. When the temperature exceeds a predetermined threshold value, the overheat protection circuit 32 regards it as abnormal and reduces the temperature (so that the amount of power supply decreases). The drive circuit 26 is controlled. The ON / OFF circuit 33 controls driving ON / OFF in the chopper regulator IC 20 based on an external signal input to the CTRL terminal.

  The output abnormality detection circuit 42 is provided on the upstream side of the LED group 50, and detects whether the output current output from the output capacitor 15 to the LED group 50 exceeds a predetermined threshold value. If the threshold is exceeded, the output current is regarded as abnormal, and the switch 41 is disconnected.

  Thus, when the output current becomes abnormal for some reason, the power supply path is interrupted by the switch 41. Therefore, it is possible to prevent a situation in which current from the DC power supply 11 side leaks to the LED group 50 or the like at the time of abnormality.

  In the present embodiment, the output abnormality detection circuit 42 detects whether or not the output current exceeds a predetermined threshold value. However, does the output voltage output to the LED group 50 exceed the predetermined threshold value? It is good also as what detects whether or not. Even in this case, if the output voltage exceeds the threshold value, it is regarded as abnormal, and the switch 41 may be disconnected.

  Further, the position where the switch 41 is arranged is not limited to that in the present embodiment, and can be any position on the path for supplying power to the LED group 50. For example, as shown in FIG. 2, a switch 41 may be disposed between the DC power supply 11 and the branch point of the input capacitor 12 and the coil 13.

[Example 2]
Next, as a second embodiment of the present invention, an LED driver having a boost chopper regulator circuit will be described. The present embodiment is basically the same in configuration as the first embodiment except that a feedback voltage detection circuit is provided instead of the output abnormality detection circuit, and thus a duplicate description is omitted.

  FIG. 3 shows a configuration diagram of the LED driver device. As described above, in this embodiment, the FB (feedback) voltage detection circuit 43 connected to the downstream side of the LED group 50 is provided, so that the error amplifier 29 is input from the downstream side of the LED group 50. The voltage (feedback voltage) is monitored. Then, the FB voltage detection circuit 43 determines whether or not the feedback voltage exceeds a predetermined threshold value. If the feedback voltage exceeds the threshold value, the FB voltage detection circuit 43 sets the switch in a disconnected state.

  As a result, when the feedback voltage becomes abnormal for some reason, the power supply path is interrupted by the switch 41. Therefore, it is possible to prevent a situation in which current from the DC power supply 11 side leaks to the LED group 50 or the like at the time of abnormality.

  As described above, in this embodiment, the switching of the switch 41 is controlled based on the status of the feedback voltage by providing the FB voltage detection circuit 43 instead of the output abnormality detection circuit 42 in the first embodiment. The output abnormality detection circuit 42 according to the first embodiment and the FB voltage detection circuit 43 according to the present embodiment are not mutually exclusive, and both may be provided.

[Example 3]
Next, as a third embodiment of the present invention, an LED driver having a boost chopper regulator circuit will be described. The present embodiment is basically the same in configuration as the first embodiment except that an input current detection circuit is provided instead of the output abnormality detection circuit, and thus a duplicate description is omitted.

  FIG. 4 shows a configuration diagram of the LED driver according to the present embodiment. As described above, the LED driver is provided with the input current detection circuit 44. The input current detection circuit 44 is provided between the DC power supply 11 and the coil 13 and detects the magnitude of the current (input current) flowing from the DC power supply 11 to the coil side. If the magnitude of this current exceeds a predetermined threshold, the switch 41 is disconnected.

  As a result, when the input current becomes abnormal for some reason, the power supply path is cut off by the switch 41. Therefore, it is possible to prevent a situation in which current from the DC power supply 11 side leaks to the LED group 50 or the like at the time of abnormality.

  As described above, in this embodiment, the input current detection circuit 44 is provided instead of the output abnormality detection circuit 42 in the first embodiment, so that the switching of the switch 41 is controlled based on the state of the input current. The output abnormality detection circuit 42 according to the first embodiment and the input current detection circuit 44 according to the present embodiment are not mutually exclusive, and both may be provided.

[Example 4]
Next, as a fourth embodiment of the present invention, an LED driver having a boost chopper regulator circuit will be described. The present embodiment is basically the same in configuration as the first embodiment except that a switch current detection circuit is provided instead of the output abnormality detection circuit, and thus a duplicate description is omitted.

  FIG. 5 shows a configuration diagram of the LED driver according to the present embodiment. Thus, the LED driver is provided with the SW (switch) current detection circuit 45. The SW current detection circuit 45 is provided on a path from the rear stage of the coil 13 to the switching transistors (21a, 21b), and current (switching current) flowing from the rear stage side of the coil 13 to the switching transistors (21a, 21b). ) Is detected. If the magnitude of this current exceeds a predetermined threshold, the switch 41 is disconnected.

  As a result, when the switching current becomes abnormal for some reason, the power supply path is interrupted by the switch 41. Therefore, it is possible to prevent a situation in which current from the DC power supply 11 side leaks to the LED group 50 or the like at the time of abnormality.

  As described above, in this embodiment, the switching of the switch 41 is controlled based on the state of the switching current by providing the SW current detection circuit 45 instead of the output abnormality detection circuit 42 in the first embodiment. The output abnormality detection circuit 42 according to the first embodiment and the SW current detection circuit 45 according to the present embodiment are not mutually exclusive, and both may be provided.

[Example 5]
Next, as a fifth embodiment of the present invention, an LED driver having a boost chopper regulator circuit will be described. The present embodiment is basically the same in configuration as the first embodiment except that a coil temperature detection circuit is provided instead of the output abnormality detection circuit, and therefore a duplicate description is omitted.

  FIG. 6 shows a configuration diagram of the LED driver according to the present embodiment. As described above, the LED driver is provided with the coil temperature detection circuit 46. The coil temperature detection circuit 46 includes a temperature sensor, and is disposed so as to be in contact with the coil 13 or very close to the coil 13. As a result, the coil temperature detection circuit 46 can detect the temperature of the coil 13 (or the temperature in the vicinity of the coil 13).

  When the detected temperature exceeds a predetermined threshold value, the coil temperature detection circuit 46 sets the switch 41 in a disconnected state. As a result, when the temperature of the coil 13 becomes abnormal for some reason, the power supply path is blocked by the switch 41. Therefore, it is possible to prevent a situation in which current from the DC power supply 11 side leaks to the LED group 50 or the like at the time of abnormality. When excessive power is supplied to the circuit, it is normal for the temperature of the circuit to rise abnormally due to Joule heat, etc. It is possible to detect.

  As described above, in this embodiment, the switching of the switch 41 is controlled based on the temperature state of the coil 13 by providing the coil temperature detection circuit 46 instead of the output abnormality detection circuit 42 in the first embodiment. . The output abnormality detection circuit 42 according to the first embodiment and the coil temperature detection circuit 46 according to the present embodiment are not mutually exclusive, and both may be provided.

  Further, in the present embodiment, the abnormality in the power supply is detected by paying attention to the temperature of the coil 13, but the present invention is not limited to this, and an abnormal situation is detected by detecting the temperature in other places. You may do it. For example, as shown in FIG. 7, a diode temperature detection circuit 49 for detecting the temperature of the output diode 14 (or a temperature in the vicinity of the output diode) is provided, and the switch 41 is controlled based on the detection result. Also good.

[Example 6]
Next, as a sixth embodiment of the present invention, an LED driver having a boost chopper regulator circuit will be described. The present embodiment is basically the same configuration as the first embodiment except that the switch is omitted, and a synchronous rectification method is adopted by providing a rectifying FET instead of a diode. A duplicate description is omitted.

  FIG. 8 shows a configuration diagram of the LED driver of this embodiment. As shown in the figure, the LED driver is provided with a rectifying FET 47. The source of the rectifying FET 47 is connected to the rear stage side of the coil 13, and the drain is connected to the front stage side of the LED group 50 and the output abnormality detection circuit 42. That is, instead of the output diode 14 in the first embodiment, a rectifying FET 47 is provided.

  On the other hand, a synchronous rectification drive circuit 34 is employed in the present embodiment as an equivalent to the drive circuit 26 in the first embodiment. The synchronous rectification drive circuit 34 controls the switching transistors (21a, 21b) according to the output of the PWM comparator 28, and outputs a control signal to the gate of the rectification FET 47, thereby realizing a synchronous rectification operation. Since the synchronous rectification method itself is a known technique, its detailed description is omitted.

  The output abnormality detection circuit 42 is provided on the upstream side of the LED group 50, and detects whether or not the output current (or output voltage) output to the LED group 50 exceeds a predetermined threshold value. When the threshold value is exceeded, the output current (or output voltage) is regarded as abnormal, and the source-drain of the rectifying FET 47 is turned off. More specifically, the output abnormality detection circuit 42 instructs the synchronous rectification drive circuit 34 to make the source and drain of the rectification FET 47 non-conductive. Then, the synchronous rectification drive circuit 34 adjusts the gate voltage of the rectification FET 47 so that the source and the drain become non-conductive.

  As described above, in this embodiment, the power supply path is shut off at the time of abnormality through the rectifying FET 47 instead of the switch 41. As a result, in the step-up chopper regulator circuit adopting the synchronous rectification method as in the present embodiment, it is possible to prevent current leakage as much as possible without providing an equivalent of the switch 41. ing.

  In this embodiment, the abnormal state is detected by the output abnormality detection circuit 42. In addition, as shown in FIG. 9, for example, the temperature of the rectifying FET 47 (or the temperature in the vicinity of the rectifying FET 47) is detected. It is also possible to provide an FET temperature detection circuit 48 for detecting an abnormal state. That is, when the detected temperature in the FET temperature detection circuit 48 exceeds a predetermined threshold value, the synchronous rectification drive circuit 34 may be controlled so that the source and drain of the rectification FET 47 are not conductive. .

[Summary]
As described above, the boost chopper regulator circuit according to the first to fifth embodiments of the present invention determines whether any one of the current, voltage, and temperature in the circuit exceeds a predetermined threshold value. Detecting circuit (42 to 46, 49). Further, a switch 41 is provided in a path connecting the DC power supply 11 (power supply) and the LED group 50 (load), and can switch connection / disconnection between the front side and the rear side in the path. The switch 41 is switched in accordance with the detection result in the detection circuit.

  Therefore, when an abnormality (a state in which the current in the circuit exceeds a predetermined threshold) is detected by various detection circuits, the path connecting the power source and the load can be blocked. For this reason, even when an abnormality occurs, it is possible to prevent a problem that current leaks out as much as possible.

  Further, since the switch 41 can be switched between connection and non-connection, even after the path is cut off (non-connection state), it is easy to return to the normal state by setting the switch again to the connection state. Therefore, the process of replacing the fuse is not necessary, and it is possible to avoid the loss of the convenience of the device as much as possible.

  On the other hand, the step-up chopper regulator circuit according to the sixth embodiment of the present invention employs a synchronous rectification method using an FET, and the pre-stage side and the post-stage side are non-conductive according to the detection result in the detection circuit. Thus, a cutoff means for controlling the FET is provided. For this reason, the FET used for the synchronous rectification operation is also used as a switch for switching connection / disconnection of the path connecting the power source and the load. It is possible to realize the interruption.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these, What added various modification | change is included unless it deviates from the main point of this invention. In addition, the technical matters in the embodiments can be applied in combination as long as there is no contradiction. In particular, a plurality of the detection circuits (42 to 46, 48, 49) described above can be provided in the same boost chopper regulator circuit.

  The present invention is useful in LED drivers that supply power to LEDs.

It is a block diagram of the LED driver which concerns on Example 1 of this invention. It is a block diagram of the LED driver which concerns on another form of Example 1 of this invention. It is a block diagram of the LED driver which concerns on Example 2 of this invention. It is a block diagram of the LED driver which concerns on Example 3 of this invention. It is a block diagram of the LED driver which concerns on Example 4 of this invention. It is a block diagram of the LED driver which concerns on Example 5 of this invention. It is a block diagram of the LED driver which concerns on another form of Example 5 of this invention. It is a block diagram of the LED driver which concerns on Example 6 of this invention. It is a block diagram of the LED driver which concerns on another form of Example 6 of this invention. It is a block diagram concerning an example of the conventional LED driver.

Explanation of symbols

11 DC power supply 12 Input capacitor 13 Coil 14 Output diode (rectifier element)
15 Output capacitor 16 Fuse 20 Chopper regulator IC
21a, 21b Switching transistor (switching element)
23 Comparator 24 Amplifier 25 Oscillation Circuit 26 Drive Circuit 27 Overcurrent Protection Circuit 28 PWM Comparator 29 Error Amplifier 30 Reference Voltage Source 31 Overvoltage Protection Circuit 32 Overheat Protection Circuit 33 ON / OFF Circuit 34 Synchronous Rectification Drive Circuit 41 Switch 42 Output Abnormality Detection Circuit 43 feedback voltage detection circuit 44 input current detection circuit 45 switching current detection circuit 46 coil temperature detection circuit 47 rectifying FET
48 FET temperature detection circuit 49 Diode temperature detection circuit 50 LED group (load)
R1, R2 resistance elements

Claims (14)

A coil to which the power supply is connected in the previous stage;
A rectifying element connected to the subsequent stage of the coil and having a rectifying action from the front side to the rear side;
An output terminal provided at a subsequent stage of the rectifying element and connected to a predetermined load;
A switching element that is provided on a ground path that connects an intermediate point of the coil and the rectifying element and a ground point, and that switches conduction / non-conduction of the ground path,
In the step-up chopper regulator circuit in which the power output to the load is controlled through the switching,
Detecting means for detecting whether any of current, voltage, and temperature in the circuit exceeds a predetermined threshold;
A switch that is provided in a path connecting the power source and the load, and that can switch connection / disconnection between the front side and the rear side in the path;
The step-up chopper regulator circuit is characterized in that switching of the switch is performed in accordance with a detection result in the detection means. The switch
The step-up chopper regulator circuit according to claim 1, which is provided between the rectifier element and the output terminal. The switch
The step-up chopper regulator circuit according to claim 1, wherein the step-up chopper regulator circuit is provided on a front stage side of the coil. The detection means includes
4. The step-up chopper regulator circuit according to claim 1, wherein it detects whether or not a current or voltage output to the load exceeds a predetermined threshold value. The detection means includes
The step-up chopper regulator circuit according to any one of claims 1 to 3, wherein it detects whether or not a current in a previous stage of the coil exceeds a predetermined threshold value. The detection means includes
4. The step-up chopper regulator circuit according to claim 1, wherein it detects whether or not a current in the ground path exceeds a predetermined threshold value. The detection means includes
The step-up chopper regulator circuit according to any one of claims 1 to 3, wherein whether or not the temperature of the coil exceeds a predetermined threshold value is detected. The detection means includes
The step-up chopper regulator circuit according to any one of claims 1 to 3, wherein whether or not a temperature of the rectifying element exceeds a predetermined threshold value is detected. The step-up chopper regulator circuit according to any one of claims 1 to 3, wherein a voltage at a subsequent stage of the load is fed back and the switching is controlled based on the voltage.
The detection means includes
A step-up chopper regulator circuit characterized by detecting whether or not the voltage fed back exceeds a predetermined threshold value. A coil to which the power supply is connected in the previous stage;
FET connected to the rear stage of the coil, and having a rectifying action from the front stage side to the rear stage side,
An output terminal provided at a subsequent stage of the FET and connected to a predetermined load;
A switching element provided on a ground path connecting an intermediate point between the coil and the FET and a ground point, and for switching conduction / non-conduction of the ground path,
In the step-up chopper regulator circuit in which the power output to the load is controlled through the switching, and the synchronous rectification method using the FET is adopted.
Detecting means for detecting whether any of current, voltage, and temperature in the circuit exceeds a predetermined threshold;
According to the detection result in the detection means, a blocking means for controlling the FET so that the front side and the rear side are non-conductive,
A step-up chopper regulator circuit comprising: The detection means includes
The step-up chopper regulator circuit according to claim 10, wherein whether or not the temperature of the FET exceeds a predetermined threshold value is detected. In the chopper regulator circuit that adjusts the power obtained from the power supply and supplies it to a predetermined load,
Detecting means for detecting whether any of current, voltage, and temperature in the circuit exceeds a predetermined threshold;
A switch that is provided in a path connecting the power source and the load, and that can switch connection / disconnection between the front side and the rear side in the path;
The step-up chopper regulator circuit is characterized in that switching of the switch is performed in accordance with a detection result in the detection means. While adjusting the power obtained from the power supply and supplying it to a predetermined load,
In a boost chopper regulator circuit to which a synchronous rectification method using a rectifying FET is applied,
Detecting means for detecting whether any of current, voltage, and temperature in the circuit exceeds a predetermined threshold;
According to the detection result in the detection means, a blocking means for controlling the FET so that the front side and the rear side are non-conductive,
A step-up chopper regulator circuit comprising:   An electronic apparatus using the step-up chopper regulator circuit according to any one of claims 1 to 13.

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