JP2005073460A - Switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a switching power supply from being damaged by an input excess voltage, and to suppress the withstand voltage of a switching element to a low value. <P>SOLUTION: The switching power supply includes a rising rate calculator 18B which calculates the difference (voltage rising rate) between a voltage value of an input voltage Vi detected by an input voltage detector 18A and a voltage value detected before the previous voltage value is detected, a rising rate comparator 18C which compares a voltage rising rate with a predetermined reference rising rate. An operation stop signal setter 18E switches the operation stop signal from OFF state to ON sate, when the voltage rising rate exceeds a predetermined reference rising rate. A controller stops the switching operation of a switching element 12, when the operation stop signal is an ON state. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a switching power supply device.

In the switching power supply described in Patent Document 1 below, when the detected input voltage (output voltage) exceeds a predetermined threshold voltage, it is determined that the input voltage is abnormal, and the switching element is protected from the input overvoltage. Therefore, the switching operation by the switching element is stopped.
JP 2003-33015 A

  By the way, in the switching power supply device described above, since the switching operation is stopped after determining that the input voltage is abnormal, when the input voltage suddenly rises, the abnormality of the input voltage is detected. It is conceivable that the input voltage already exceeds the breakdown voltage of the switching element before the switching operation is actually stopped. In such a case, the switching power supply device may be damaged.

  Therefore, in order to solve the above-described problems, the present invention provides a switching power supply device that prevents the switching power supply device from being damaged by an input overvoltage and that can suppress the breakdown voltage of the switching element to a low level. Objective.

  The switching power supply device according to the present invention includes a switching element that switches a supplied input voltage, a control unit that controls a switching operation of the switching element, a voltage detection unit that detects a voltage value of the input voltage, and a voltage detection unit. Comparing means for comparing the voltage increase rate corresponding to the detected voltage value with a predetermined reference increase rate, and stop signal output means for outputting a stop signal for stopping the switching operation based on the comparison result by the comparing means. And the control means stops the switching operation based on the stop signal output by the stop signal output means.

  According to this invention, the switching power supply device can output the stop signal for stopping the switching operation based on the comparison result between the voltage increase rate of the input voltage and the predetermined reference increase rate, and based on this stop signal Thus, the switching operation can be stopped. Therefore, for example, when it is determined that there is an abnormality in the fluctuation of the voltage rise rate, such as when the voltage rise rate of the input voltage exceeds a predetermined reference rise rate, a stop signal for stopping the switching operation is output. It becomes possible to make it. In such a case, the switching operation can be stopped before the input voltage reaches a predetermined threshold voltage. As a result, it is possible to prevent the input voltage from exceeding the withstand voltage of the switching element between when the stop signal is output and when the switching operation is stopped. Can be prevented. Furthermore, the withstand voltage of the switching element can be kept low by adjusting the set value of the reference increase rate.

  In the switching power supply device of the present invention, the voltage increase rate is calculated by calculating a difference between the voltage value detected by the voltage detection means and the voltage value detected by the voltage detection means before the voltage value is detected. It is preferable that the above-mentioned comparison means compare the voltage increase rate calculated by the increase rate calculating means with a predetermined reference increase rate.

  In this way, the switching power supply device can calculate the voltage increase rate of the input voltage by calculating the difference between the voltage value of the input voltage detected this time and the voltage value of the input voltage detected previously. Therefore, the voltage increase rate can be obtained simply and quickly.

  In the switching power supply of the present invention, it is preferable that the stop signal output means outputs the stop signal when the signal corresponding to the comparison result indicates that the voltage increase rate is larger than a predetermined reference increase rate. .

  In this way, the switching power supply device can output a stop signal for stopping the switching operation when the voltage increase rate of the input voltage is larger than the predetermined reference increase rate. Therefore, since the stop signal for stopping the switching operation can be output when the voltage increase rate of the input voltage exceeds the predetermined reference increase rate, the time from when the stop signal is output until the switching operation is stopped. The input voltage can be prevented from exceeding the withstand voltage of the switching element.

  In the switching power supply device of the present invention, the switching power supply further includes a determination unit that determines whether or not the voltage value detected by the voltage detection unit is within a range of an allowable input voltage value, and the stop signal output unit outputs a stop signal It is preferable to output a signal for resuming the switching operation after a predetermined stop time has elapsed and when the determination unit determines that the voltage value is within the allowable input voltage value range. .

  In this way, the switching power supply device performs switching only when the voltage value of the input voltage detected after a predetermined stop time has elapsed after the stop signal is output is within the allowable input voltage value range. The operation can be resumed.

  According to the switching power supply device according to the present invention, it is possible to prevent the switching power supply device from being damaged by the input overvoltage and to suppress the breakdown voltage of the switching element to a low level.

  Hereinafter, embodiments of a switching power supply device according to the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same element and the overlapping description is abbreviate | omitted.

  FIG. 1 is a diagram illustrating an electric circuit configuration of a switching power supply device 1 according to the embodiment. The switching power supply device 1 in the present embodiment is a full-bridge type DC-DC converter. As shown in FIG. 1, the switching power supply device 1 includes a drive circuit 11, a switching element 12, a transformer 13, and a rectifier diode. 14, 15, choke coil 16, smoothing capacitor 17, operation stop determination circuit 18, and controller (control means) 19. The DC power supply 10 supplies the input voltage Vi to the switching power supply device 1.

  The switching element 12 shown in FIG. 1 is an element that switches the input voltage Vi supplied from the DC power supply 10, and corresponds to, for example, a transistor such as a field effect transistor (FET). A drive circuit 11 is connected to the gate of the switching element 12, and the drive circuit 11 drives the switching element 12 based on a drive signal output from the controller 19. The switching element 12 performs a switching operation (switching operation between an ON state and an OFF state) based on the level of the drive signal.

  The transformer 13 has a primary winding and a secondary winding. In the present embodiment, the polarity of the primary winding of the transformer 13 and the polarity of the secondary winding are positive.

  A smoothing circuit is configured by the choke coil 16 and the smoothing capacitor 17, and an output voltage Vo is generated between both ends of the smoothing capacitor 17.

  The rectifier diodes 14 and 15 rectify the secondary winding side voltage induced in the secondary winding of the transformer 13.

  The operation stop determination circuit 18 is a circuit that determines whether or not to stop the switching operation based on the voltage value of the input voltage supplied from the DC power supply 10.

  Here, the functional configuration of the operation stop determination circuit 18 will be described with reference to FIG. As shown in FIG. 2, the operation stop determination circuit 18 includes an input voltage detection unit (voltage detection unit) 18A, an increase rate calculation unit (increase rate calculation unit) 18B, an increase rate comparison unit (comparison unit) 18C, and an allowable voltage determination unit. (Decision means) 18D and an operation stop signal setting section (stop signal output means) 18E. Each of these units is a functional element realized by a microprocessor such as a DSP (Digital Signal Processor).

  2 detects the voltage value of the input voltage Vi at a predetermined sampling interval (for example, 1 [μS]).

  The increase rate calculation unit 18B calculates the difference between the voltage value of the input voltage Vi detected by the input voltage detection unit 18A and the voltage value detected before the voltage value is detected, and the calculated difference value Is the voltage increase rate (voltage fluctuation rate) of the input voltage Vi.

  The increase rate comparison unit 18C compares the voltage increase rate of the input voltage Vi calculated by the increase rate calculation unit 18B with a predetermined reference increase rate, and outputs a signal corresponding to the comparison result. Specifically, the increase rate comparison unit 18C outputs a high level (ON state) signal when the voltage increase rate of the input voltage Vi exceeds a predetermined reference increase rate, and the voltage of the input voltage Vi When the increase rate is equal to or less than a predetermined reference increase rate, a low level (OFF state) output signal is output. The reference increase rate is set in advance based on the specifications of the switching element 12.

  The allowable voltage determination unit 18D determines whether or not the voltage value of the input voltage Vi detected by the input voltage detection unit 18A is within the range of the allowable input voltage value. This allowable input voltage value is set in advance based on the specifications of the switching element 12.

  The operation stop signal setting unit 18E sets an output state of an operation stop signal indicating whether or not to stop the switching operation. More specifically, the operation stop signal setting unit 18E is configured such that when the signal output from the increase rate comparison unit 18C is switched from the OFF state to the ON state, that is, the voltage increase rate of the input voltage Vi is a predetermined reference increase. When the rate is exceeded, the operation stop signal is switched from the OFF state to the ON state. The operation stop signal setting unit 18E is after the predetermined stop time has elapsed since the operation stop signal was set to the ON state, and the determination result by the allowable voltage determination unit 18D is that the voltage value of the input voltage Vi is an allowable input. When indicating that the voltage is within the range, the operation stop signal is switched from the ON state to the OFF state. The operation stop signal setting unit 18E sets the operation stop signal to the OFF state when the determination result by the allowable voltage determination unit 18D indicates that the voltage value of the input voltage Vi is outside the range of the allowable input voltage value. Wait until the next stop time elapses without switching. Further, the predetermined stop time may be equal to or longer than a predetermined sampling interval for detecting the voltage value of the input voltage Vi.

  The controller 19 shown in FIG. 1 generates and outputs a drive signal for controlling the switching operation of the switching element 12 based on the target voltage that is the target value of the output voltage Vo and the output voltage Vo. The controller 19 generates a signal for stopping the switching operation of the switching element 12 when the operation stop signal received from the operation stop determination circuit 18 is in the ON state. When the operation stop signal received from the operation stop determination circuit 18 is switched from the ON state to the OFF state, the controller 19 generates a signal for resuming the switching operation of the switching element 12.

  Next, with reference to the timing chart shown in FIG. 3, a signal flow when stopping the switching operation based on the rate of increase of the input voltage Vi will be described.

  FIG. 3A is a diagram showing a pulse waveform of the input voltage Vi supplied from the DC power supply 10. In addition, a1 shown by Fig.3 (a) is a waveform which shows the upper limit threshold signal of the input allowable range of the input voltage Vi, and a2 is a waveform which shows the lower limit threshold signal of the input allowable range of the input voltage Vi. FIG. 3B is a diagram illustrating a waveform of a sampling pulse that is a timing for detecting the input voltage Vi. FIG. 3C is a diagram illustrating a pulse waveform of the voltage increase rate of the input voltage Vi output from the increase rate calculation unit 18B. In addition, c1 shown by FIG.3 (c) is a waveform which shows the signal of the reference | standard raise rate of the input voltage Vi. FIG. 3D is a diagram illustrating a pulse waveform of a signal corresponding to the comparison result of the increase rate output from the increase rate comparison unit 18C. FIG. 3E is a diagram illustrating a pulse waveform of the operation stop signal output from the operation stop signal setting unit 18E. Note that the horizontal axis of the timing chart shown in FIG. 3 indicates time [t].

  First, when the sampling pulse rises to the ON state at time t1 (FIG. 3B), the input voltage detection unit 18A detects the voltage value of the input voltage Vi (FIG. 3A), and the rate of increase calculation unit 18B. Is a signal indicating the voltage increase rate by calculating the voltage increase rate of the input voltage Vi based on the voltage value of the input voltage Vi detected at time t1 and the voltage value of the input voltage Vi detected at time t0. It outputs (FIG.3 (c)). The time t0 is the rise time of the sampling signal that is turned on immediately before the sampling signal that rises at the time t1. However, the voltage value to be calculated when calculating the voltage increase rate is not necessarily the voltage value sampled immediately before. For example, it may be a voltage value sampled before a predetermined time. In short, it is only necessary to detect a rapid voltage increase rate that appears in the event of an abnormality.

  Further, at time t1, the increase rate comparison unit 18C compares the voltage increase rate of the input voltage Vi (FIG. 3C) calculated by the increase rate calculation unit 18B with the reference increase rate C1, and displays the comparison result. A corresponding signal is output (FIG. 3 (d)). More specifically, at time t1, as shown in FIG. 3C, the voltage increase rate of the input voltage Vi exceeds the reference increase rate c1, so the increase rate comparison unit 18C sets the output signal to the ON state. (FIG. 3D).

  In this way, when the signal output from the increase rate comparison unit 18C switches from the OFF state to the ON state at time t1 (FIG. 3D), the operation stop signal setting unit 18E turns the operation stop signal from the OFF state to ON. The state is switched (FIG. 3E). As a result, the switching operation of the switching element 12 is forcibly stopped by the controller 19 that receives this operation stop signal.

  Next, at time t2, when the voltage increase rate of the input voltage Vi changes to less than the reference increase rate c1 as shown in FIG. 3C, the increase rate comparison unit 18C switches the output signal from the ON state to the OFF state. (FIG. 3 (d)). Even if the voltage increase rate of the input voltage Vi changes to less than the reference increase rate c1 at time t2, the switching operation of the switching element 12 is not resumed because the operation stop signal shown in FIG. .

  Next, when a predetermined stop time elapses from time t1 and time t3 is reached, the operation stop signal setting unit 18E switches the operation stop signal from the ON state to the OFF state based on the determination result by the allowable voltage determination unit 18D. (FIG. 3 (e)). At time t3, as shown in FIG. 3A, since the voltage value of the input voltage Vi is within the range of the allowable input voltage values a1 and a2, the operation stop signal setting unit 18E outputs the operation stop signal. It will be switched from the ON state to the OFF state. As a result, the switching operation of the switching element 12 is resumed by the controller 19 that receives this operation stop signal.

  As described above, the switching power supply device 1 according to the present embodiment includes the input voltage detection unit 18A, the increase rate comparison unit 18C, and the operation stop signal setting unit 18E, whereby the voltage increase rate of the input voltage and a predetermined reference increase are provided. A stop signal for stopping the switching operation can be output based on the comparison result with the rate. Therefore, it is possible to output a stop signal for stopping the switching operation when the voltage increase rate of the input voltage exceeds a predetermined reference increase rate. That is, it is possible to output a stop signal for stopping the switching operation when it is determined that there is an abnormality in the fluctuation of the voltage increase rate. Further, since the controller 19 stops the switching operation based on the stop signal output from the operation stop signal setting unit 18E, the input voltage is a predetermined threshold voltage (a voltage value set based on the specifications of the switching element 12). The switching operation can be stopped before reaching. As a result, it is possible to prevent the input voltage from exceeding the withstand voltage of the switching element 12 between the output of the stop signal and the stop of the switching operation. Therefore, the switching power supply device 1 is damaged by the input overvoltage. It becomes possible to prevent that. Furthermore, the withstand voltage of the switching element can be kept low by adjusting the set value of the reference increase rate.

  Further, in the switching power supply device 1 according to the present embodiment, the increase rate calculation unit 18B calculates the input voltage by calculating the difference between the voltage value detected this time by the input voltage detection unit 18A and the voltage value previously detected. Therefore, it is possible to calculate the voltage increase rate simply and quickly.

  Further, in the switching power supply device 1 according to the present embodiment, the operation stop signal setting unit 18E is after the predetermined stop time has elapsed since the last output of the stop signal and the allowable voltage determination unit 18D When it is determined that the value is within the allowable input voltage value range, a signal for restarting the switching operation is output. Therefore, the input voltage detected after a predetermined stop time has elapsed since the stop signal was output. Only when the voltage value is within the range of the allowable input voltage value, the switching operation can be resumed.

  Note that the present invention prevents the switching element from being damaged by the input overvoltage between the time when the detected voltage fluctuation is detected and the time when the switching operation actually stops. It is characterized by controlling the switching operation. Therefore, the present invention is not limited to the above-described embodiment. For example, the following modifications are possible.

  The switching power supply device in the above-described embodiment is a full-bridge type DC-DC converter, but the switching power supply device is not limited to this. For example, a forward type, a flyback type, a push-pull type, Even a DC-DC converter such as a half-bridge type is applicable. Further, it is applicable to either an insulating type or a non-insulating type.

  Further, the input voltage detection unit 18A in the above-described embodiment detects the voltage value of the input voltage Vi supplied from the DC power supply 10, but the detected voltage is not limited to the input voltage Vi. The present invention is also applicable when detecting the output voltage Vo.

  Further, although the input voltage detection unit 18A and the increase rate comparison unit 18C in the above-described embodiment have been described as functional elements realized by a microprocessor such as a DSP, these functions may be realized by an analog circuit. . For example, it may be configured by a differentiating circuit, the input voltage Vi is differentiated by the differentiating circuit, the inclination of the input voltage Vi is detected, and the detected inclination is compared with a reference value.

  Further, although the operation stop determination circuit 18 in the above-described embodiment has been described as a component different from the controller 19, the operation stop determination circuit 18 may be included in the component of the controller 19.

It is a figure which shows the electric circuit structure of the switching power supply device in embodiment. It is a figure which shows the function structure of the operation stop determination circuit shown in FIG. It is a timing chart which shows the signal flow at the time of stopping switching operation | movement based on the increase rate of an input voltage.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Switching power supply device, 10 ... DC power supply, 11 ... Drive circuit, 12 ... Switching element, 13 ... Transformer, 14, 15 ... Rectifier diode, 16 ... Choke coil , 17 ... smoothing capacitor, 18 ... operation stop determination circuit, 18A ... input voltage detection unit, 18B ... increase rate calculation unit, 18C ... increase rate comparison unit, 18D ... allowable voltage Judgment part, 18E ... Operation stop signal setting part, 19 ... Controller.

Claims (4)

A switching element for switching the supplied input voltage;
Control means for controlling the switching operation of the switching element;
Voltage detecting means for detecting a voltage value of the input voltage;
Comparison means for comparing a voltage increase rate corresponding to the voltage value detected by the voltage detection means with a predetermined reference increase rate;
A stop signal output means for outputting a stop signal for stopping the switching operation based on a comparison result by the comparison means;
The control means stops the switching operation based on the stop signal outputted by the stop signal output means. An increase rate calculation that calculates the voltage increase rate by calculating a difference between the voltage value detected by the voltage detection unit and the voltage value detected by the voltage detection unit before the voltage value is detected. Further comprising means,
2. The switching power supply device according to claim 1, wherein the comparison unit compares the voltage increase rate calculated by the increase rate calculation unit with the predetermined reference increase rate.   The stop signal output means outputs the stop signal when a signal corresponding to the comparison result indicates that the voltage increase rate is larger than the predetermined reference increase rate. Or the switching power supply device of Claim 2. A determination unit for determining whether or not the voltage value detected by the voltage detection unit is within a range of an allowable input voltage value;
The stop signal output means is after a predetermined stop time has elapsed since the stop signal was output and when the determination means determines that the voltage value is within the allowable input voltage value range The switching power supply device according to any one of claims 1 to 3, wherein a signal for resuming the switching operation is output.

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