CN112311240A - Switching power supply device - Google Patents
Switching power supply device Download PDFInfo
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- CN112311240A CN112311240A CN202010703017.9A CN202010703017A CN112311240A CN 112311240 A CN112311240 A CN 112311240A CN 202010703017 A CN202010703017 A CN 202010703017A CN 112311240 A CN112311240 A CN 112311240A
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- 238000004804 winding Methods 0.000 claims abstract description 142
- 238000001514 detection method Methods 0.000 claims abstract description 130
- 238000009413 insulation Methods 0.000 claims abstract description 17
- 238000002360 preparation method Methods 0.000 claims 2
- 230000005856 abnormality Effects 0.000 description 22
- 239000003990 capacitor Substances 0.000 description 11
- 230000007423 decrease Effects 0.000 description 11
- 238000002955 isolation Methods 0.000 description 10
- 238000010586 diagram Methods 0.000 description 3
- 238000009499 grossing Methods 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- 230000002159 abnormal effect Effects 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000013021 overheating Methods 0.000 description 2
- 238000009529 body temperature measurement Methods 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC converters
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention provides a switching power supply device, which has a simple circuit structure and can accurately protect against abnormity. A switching power supply device (100) is provided with a converter (102), a control unit (9), a switching circuit (20), an insulating transformer (21), a1 st rectifying circuit (22), a2 nd rectifying circuit (23), and an overheat detection circuit (29). When the switching element of the switching circuit is in an overheated state, the overheat detection circuit detects the overheat state and outputs a stop signal for stopping the switching operation of the switching circuit (S4). The control unit determines whether the output of the converter is short-circuited or the output of the converter is low voltage, based on a result of comparison between a change in the output voltage of a1 st rectifier circuit connected to the main winding of the insulation transformer and a change in the output voltage of a2 nd rectifier circuit connected to the auxiliary winding of the insulation transformer, and executes control for outputting short-circuit protection or low-voltage protection based on the determination result.
Description
Technical Field
The present invention relates to a switching power supply device having a DC-DC converter that steps down or up a DC voltage.
Background
For example, an electric vehicle or a hybrid vehicle is equipped with a high-voltage battery for driving a motor for traveling, and a power supply device for stepping down the voltage of the battery and supplying the stepped-down voltage to each unit. As the power supply device, a switching power supply device having a DC-DC converter that switches a DC voltage to convert the DC voltage into an ac voltage and rectifies the ac voltage to convert the ac voltage into a DC voltage having a predetermined voltage value is generally used.
Such a switching power supply device has the following functions: when an abnormality occurs due to an overcurrent or overvoltage, the abnormality is detected to protect the circuit. For example, a switching power supply device of patent document 1 is provided with an input current detection circuit, an input voltage detection circuit, and an output voltage detection circuit. Then, the value of the output current is estimated from the values of the input current, the input voltage, and the output voltage detected by the respective detection circuits, and it is determined whether or not a failure has occurred in consideration of the output current in addition to the output voltage.
In addition, the switching power supply device of patent document 2 is provided with an overcurrent protection circuit including a current detection circuit and a1 st switching element, and an overvoltage protection circuit including a voltage detection circuit and a2 nd switching element. When the current flowing through the switching element is excessive, the 1 st switching element is turned on, and the overcurrent protection circuit forcibly turns off the switching element to stop the primary dc power supply circuit, thereby protecting the switching element from the overcurrent. When the secondary dc power supply voltage becomes equal to or higher than the set voltage value, the 2 nd switching element is turned on, and the overvoltage protection circuit forcibly turns off the switching element to stop the primary dc power supply circuit, thereby protecting the switching element from the overvoltage.
Patent document 1: japanese laid-open patent publication No. 2007-97368
Patent document 2: japanese laid-open patent publication No. 7-213051
Among the abnormalities occurring in the switching power supply device, there are current abnormalities (overcurrent) caused by short-circuiting, voltage abnormalities (output voltage drop) caused by circuit disconnection, failure, and the like, and also overheat abnormalities in which the switching element abnormally generates heat and becomes a high temperature. In order to detect such various abnormalities and protect the abnormality, conventionally, a current detection circuit, a voltage detection circuit, and an overheat detection circuit are provided according to the type of abnormality, and a detection signal output from each detection circuit is transmitted to a control unit, and the control unit determines the presence or absence of the abnormality and the type of the abnormality, and executes control for protecting the abnormality. However, this requires the number of detection circuits of the abnormal type, which results in a problem that the circuit configuration becomes complicated.
Disclosure of Invention
The invention provides a switching power supply device which has a simple circuit structure and can accurately protect against an abnormality.
The switching power supply device of the present invention includes: a converter that switches an input dc voltage and converts the dc voltage into a dc voltage having a predetermined voltage value; and a control unit for controlling the operation of the converter. The converter includes: a switching circuit that switches a direct-current voltage; a drive circuit that drives the switch circuit; a rectifier circuit that rectifies the voltage that is switched and converted into alternating current; and an insulation transformer provided between the switching circuit and the rectifying circuit. The secondary winding of the insulation transformer is composed of a main winding and an auxiliary winding, and the rectifier circuit is composed of a1 st rectifier circuit and a2 nd rectifier circuit, wherein the 1 st rectifier circuit is arranged between the main winding and the output terminal of the converter, and the 2 nd rectifier circuit is connected with the auxiliary winding. In addition, the following circuits are provided: a1 st voltage detection circuit which detects an output voltage of the 1 st rectifier circuit; a2 nd voltage detection circuit that detects an output voltage of the 2 nd rectifier circuit; an overheat detection circuit that detects an overheat state of the switching element; and a feedback circuit that performs feedback control on the drive circuit so that the output voltage of the converter becomes a target value. The overheat detection circuit outputs a stop signal for stopping the switching operation of the switching circuit to perform overheat protection when the temperature of the switching element exceeds a threshold value. The control unit determines whether the output of the converter is short-circuited or the output of the converter is low voltage based on a result of comparison between the change in the voltage detected by the 1 st voltage detection circuit and the change in the voltage detected by the 2 nd voltage detection circuit, and executes control for outputting short-circuit protection or low-voltage protection based on the determination result.
In this way, when the switching element is in the overheat state, the overheat protection can be performed by stopping the switching operation of the switching circuit without passing through the control unit by the stop signal output from the overheat detection circuit. The control unit can determine that the output of the converter is short-circuited or the voltage drops by comparing the changes in the detection voltages of the 1 st voltage detection circuit and the 2 nd voltage detection circuit. Therefore, an interface circuit or the like is not required between the overheat detection circuit and the control unit, and an overcurrent detection circuit for short-circuit detection is not required, thereby simplifying the circuit configuration. In addition, although the circuit configuration is simple, protection can be accurately performed in accordance with the type of abnormality.
In the present invention, the control unit executes the following processing, for example.
A. When the respective detection voltages rise after a state in which the voltage detected by the 1 st voltage detection circuit is lower than the normal voltage and the voltage detected by the 2 nd voltage detection circuit is lower than the normal voltage continues for a certain time and before a predetermined 1 st time elapses, it is determined that the overheat detection circuit has performed the overheat protection.
B. When the state in which the voltage detected by the 1 st voltage detection circuit is lower than the normal voltage and the voltage detected by the 2 nd voltage detection circuit is higher than the normal voltage continues for a predetermined 2 nd time, it is determined that a short circuit has occurred in the output of the converter, and control for output short-circuit protection is executed.
C. When the 1 st voltage detection circuit detects a voltage lower than the normal voltage and the 2 nd voltage detection circuit detects a voltage lower than the normal voltage for a3 rd time longer than the 1 st time, it is determined that the output of the converter is a low voltage, and control for outputting a low voltage protection is performed.
In the present invention, the control unit may have only the functions of a and B, A and C or B and C among a to C.
In the present invention, the control unit may stop the switching operation of the switching circuit and perform output short-circuit protection by outputting the permission signal when the switching operation of the switching circuit is permitted, and stopping the permission signal or outputting a prohibition signal different from the permission signal when it is determined that the output of the converter is short-circuited.
In the present invention, the control unit may stop the permission signal or the output prohibition signal when the number of times the short-circuit occurs in the output of the converter reaches a predetermined number of times.
In the present invention, the control unit may output the failure detection signal as control for outputting the low voltage protection.
According to the switching power supply device of the present invention, the circuit configuration is simple and the protection against the abnormality can be performed accurately.
Drawings
Fig. 1 is a block diagram showing an example of a switching power supply device of the present invention.
Fig. 2 is a circuit diagram of a main portion of fig. 1.
Fig. 3 is a flowchart showing an operation of the switching power supply device at the time of overheat protection.
Fig. 4 is a timing chart showing changes in the respective winding voltages at the time of overheat protection.
Fig. 5 is a flowchart showing an operation of the switching power supply device at the time of outputting the short-circuit protection.
Fig. 6 is a timing chart showing changes in the respective winding voltages at the time of outputting the short-circuit protection.
Fig. 7 is a flowchart showing an operation of the switching power supply device when outputting the low voltage protection.
Fig. 8 is a timing chart showing changes in the voltages of the respective windings at the time of outputting the low voltage protection.
Fig. 9 is a table showing a relationship among a circuit state, a protection function, and a winding voltage in the switching power supply device.
Fig. 10 is a circuit diagram of a main part of a switching power supply device of a comparative example.
Description of the reference symbols
9: a control unit; 20: a switching circuit; 21: an insulating transformer; 22: a first rectifying circuit; 23: a2 nd rectifying circuit; 24: a1 st voltage detection circuit; 25: a2 nd voltage detection circuit; 27: a PWM circuit (drive circuit); 28: a feedback circuit; 29: an overheat detection circuit; 100: a switching power supply device; 101: a1 st converter; 102: a2 nd converter; k: a temperature measuring element; la: a primary winding; lb: a secondary winding (main winding); lc: a secondary winding (auxiliary winding); t5, T6: an output terminal; q3: a switching element; s2: a permission signal; s4: a stop signal; va: a main winding voltage; vb: an auxiliary winding voltage; x: time 1; y: time 2; z: time 3.
Detailed Description
Embodiments of the present invention will be described with reference to the accompanying drawings. Hereinafter, a switching power supply device mounted on a vehicle such as a four-wheel automobile is exemplified.
In fig. 1, the switching power supply device 100 has input terminals T1, T2, output terminals T3, T4, output terminals T5, T6, a1 st converter 101, and a2 nd converter 102.
The 1 st converter 101 is a DC-DC converter on the main side, converts a DC voltage Vi input to input terminals T1 and T2 into a DC voltage V1 having a predetermined voltage value, and outputs the DC voltage V1 to output terminals T3 and T4. The 2 nd converter 102 is a DC-DC converter on the secondary side, converts the DC voltage Vi input to the input terminals T1, T2 into a DC voltage V2 having a voltage value different from the predetermined voltage value described above, and outputs the DC voltage V2 to the output terminals T5, T6.
For example, the input voltage Vi to the input terminals T1 and T2 is 200V, the output voltage V1 to the output terminals T3 and T4 is 12V, and the output voltage V2 to the output terminals T5 and T6 is 10V. That is, in this example, the 1 st converter 101 and the 2 nd converter 102 are both step-down DC-DC converters that convert a high voltage into a low voltage.
The input terminal T1 is connected to the positive electrode of a battery (not shown) to which a dc voltage Vi is supplied, and the input terminal T2 is connected to the negative electrode of the battery. The output terminals T3 and T4 are connected to a load that operates using the output voltage V1 as a power supply, a battery that is charged by the output voltage V1, and the like (not shown). The output terminals T5 and T6 are connected to a control circuit or the like (not shown) that operates with the output voltage V2 as a power supply. The output terminal T4 and the output terminal T6 of the terminals T1 to T6 are electrically connected to the outside of the switching power supply device 100, and are grounded to a common ground terminal (not shown).
The switching power supply device 100 further includes a voltage detection circuit 6, a power supply circuit 7, a standby control circuit 8, a control unit 9, and diodes D1 and D2.
The voltage detection circuit 6 is provided between the output terminal T3 and the control unit 9, and detects the output voltage V1 of the 1 st converter 101. The power supply circuit 7 is provided between the standby control circuit 8 and the control unit 9, and normally supplies a power supply voltage to the control unit 9 based on the output voltage V1. The standby control circuit 8 is provided between the output terminal T5 and the power supply circuit 7, and supplies the output voltage V2 of the 2 nd converter 102 to the power supply circuit 7 as a standby power supply when the output voltage V1 of the 1 st converter 101 disappears or falls below a predetermined value due to disconnection or a failure.
The diode D1 is provided between the output terminal T3 and the power supply circuit 7, and forms a supply path for supplying the output voltage V1 of the 1 st converter 101 to the power supply circuit 7. The diode D2 is provided between the backup control circuit 8 and the power supply circuit 7, and forms a supply path for supplying the backup power supply (output voltage V2) from the backup control circuit 8 to the power supply circuit 7.
The control unit 9 is constituted by a microcomputer, and controls the operations of the 1 st converter 101, the 2 nd converter 102, and the standby control circuit 8. An external signal S1 is input to the control unit 9 from an external device such as an in-vehicle ECU (electronic control unit). The external signal S1 is a signal requesting the 2 nd converter 102 to operate. In addition, the control unit 9 receives the external signal S1 and outputs the permission signal S2 to the 2 nd converter 102. The permission signal S2 is a signal for permitting the 2 nd converter 102 to perform a switching operation. When the voltage detection circuit 6 detects that the output voltage V1 has become less than the predetermined value, the control unit 9 outputs the standby command signal S3 to the standby control circuit 8. The standby command signal S3 is a signal for turning on a switching element (not shown) included in the standby control circuit 8.
The 1 st converter 101 includes an input filter 1, a switching circuit 2, an isolation transformer 3, a rectifier circuit 4, and a smoothing circuit 5. Since the structures of these parts are well known and the 1 st converter 101 itself has no direct relation to the present invention, detailed description of the 1 st converter 101 is omitted. The 1 st converter 101 of this example is an insulation type DC-DC converter having an input side and an output side insulated by an insulation transformer 3.
The 2 nd converter 102 includes a switching circuit 20, an isolation transformer 21, a1 st rectifier circuit 22, a2 nd rectifier circuit 23, an isolation circuit 26, a PWM (Pulse Width Modulation) circuit 27, a feedback circuit 28, and an overheat detection circuit 29. As described above, the 2 nd converter 102 has a function of stepping down and outputting the dc voltage Vi input to the input terminals T1 and T2, and a function of supplying the backup power to the power supply circuit 7 when the 1 st converter 101 has an output abnormality. The 2 nd converter 102 in this example is also an insulation type DC-DC converter having its input side and output side insulated by an insulation transformer 21.
Fig. 2 shows a specific circuit of the switching circuit 20, the insulation transformer 21, the 1 st rectification circuit 22, and the 2 nd rectification circuit 23 of the 2 nd converter 102. The circuit shown here is an example, and the present invention is not limited to this. In fig. 2, the isolation circuit 26 in the block constituting the 2 nd converter 102 of fig. 1 is omitted.
The switching circuit 20 includes a switching element Q3 and a temperature measuring element K. In this example, the switching element Q3 is an FET (field effect transistor) and is connected between the primary winding La of the insulation transformer 21 and the ground. The gate of the switching element Q3 is connected to the PWM circuit 27, and the switching element Q3 performs an on/off operation in accordance with a PWM signal supplied from the PWM circuit 27 to the gate. The temperature measuring element K is composed of, for example, a thermistor, is disposed in the vicinity of the switching element Q3, and detects the temperature of the switching element Q3. The output (detected temperature) of the temperature measuring element K is sent to an overheat detection circuit 29 described later.
The insulation transformer 21 has a primary winding La and secondary windings Lb, Lc. In the secondary winding, the winding Lb is a main winding, and the winding Lc is an auxiliary winding. The primary winding La is connected to the switching circuit 20, the main winding Lb is connected to the 1 st rectifier circuit 22, and the auxiliary winding Lc is connected to the 2 nd rectifier circuit 23. The primary side of the isolation transformer 21 is electrically isolated from the secondary side. The input voltage Vi applied to the primary winding La is switched by turning on and off the switching element Q3 to become an ac voltage (pulse voltage), and is transmitted from the primary winding La of the isolation transformer 21 to the main winding Lb and the auxiliary winding Lc.
The 1 st rectifier circuit 22 connected to the main winding Lb includes a diode D3 and a capacitor C1, and the 1 st voltage detection circuit 24 is provided in the subsequent stage of these circuits. The diode D3 is a rectifier diode for rectifying an ac voltage generated in the main winding Lb into a dc voltage. The capacitor C1 is an output capacitor for smoothing the dc voltage rectified by the diode D3 and outputting the dc voltage from the output terminals T5 and T6. The diode D3 is connected between one end of the main winding Lb and the output terminal T5, and the capacitor C1 is connected between the output terminals T5 and T6.
The 1 st voltage detection circuit 24 is connected in parallel to the capacitor C1, and detects a voltage across the capacitor C1, that is, an output voltage of the 1 st rectifier circuit 22. This output voltage is a voltage corresponding to a voltage generated in the main winding Lb, and is therefore hereinafter referred to as "main winding voltage". The main winding voltage Va is also the output voltage V2 of the 2 nd converter 102 (Va ═ V2). The main winding voltage Va detected by the 1 st voltage detection circuit 24 is sent to the control unit 9.
The 2 nd rectifying circuit 23 connected to the auxiliary winding Lc has a diode D4 and a capacitor C2, and a2 nd voltage detecting circuit 25 is provided at the subsequent stage thereof. The diode D4 is a rectifier diode for rectifying the ac voltage generated in the auxiliary winding Lc into a dc voltage. The capacitor C2 is a capacitor for smoothing the dc voltage rectified by the diode D4.
The 2 nd voltage detection circuit 25 is connected in parallel to the capacitor C2 and detects a voltage across the capacitor C2, that is, an output voltage of the 2 nd rectifier circuit 23. This output voltage is a voltage corresponding to a voltage generated in the auxiliary winding Lc, and is therefore hereinafter referred to as "auxiliary winding voltage". The auxiliary winding voltage Vb detected by the 2 nd voltage detection circuit 25 is sent to the control section 9. In this example, no load is connected to the stage subsequent to the 2 nd rectifier circuit 23, and the 2 nd rectifier circuit 23 is provided only for detecting the auxiliary winding voltage Vb, but it is needless to say that a load may be connected to the stage subsequent to the 2 nd rectifier circuit 23.
Returning to fig. 1, the standby control circuit 8 operates in response to the standby command signal S3 output from the control unit 9. When the voltage detection circuit 6 detects that the output voltage V1 of the 1 st converter 101 disappears or falls, the control section 9 outputs a standby command signal S3. In response to this signal, a transistor (not shown) of the standby control circuit 8 is turned on, and a supply path for supplying the output voltage V2 of the 2 nd converter 102 to the power supply circuit 7 as a standby power supply is formed.
The isolation circuit 26 is a circuit for electrically isolating the permission signal S2 output from the control unit 9 and transmitting the signal to the PWM circuit 27, and is composed of an isolator.
The PWM circuit 27 receives the permission signal S2 from the isolation circuit 26, generates a PWM signal having a predetermined duty ratio, and outputs the PWM signal to the switching circuit 20. As described above, the PWM signal is supplied to the gate of the switching element Q3 (fig. 2). The feedback circuit 28 compares the output voltage V2 of the 2 nd converter 102 with a target value, and performs feedback control on the PWM circuit 27 so that the output voltage V2 becomes the target value. That is, the feedback control is performed in the following manner: when the output voltage V2 is higher than the target value, the duty ratio of the PWM signal is adjusted downward, and when the output voltage V2 is lower than the target value, the duty ratio of the PWM signal is increased. The PWM circuit 27 is an example of the "drive circuit" of the present invention.
The overheat detection circuit 29 compares the temperature of the switching element Q3 detected by the temperature measuring element K (fig. 2) with a predetermined threshold value, thereby detecting that the switching element Q3 is in an overheated state. In detail, if the detected temperature of the temperature sensing element K does not exceed the threshold value, the overheat detection circuit 29 does not detect the overheated state of the switching element Q3, and if the detected temperature of the temperature sensing element K exceeds the threshold value, the overheat detection circuit 29 detects the overheated state of the switching element Q3. When detecting the overheat state, the overheat detection circuit 29 outputs a stop signal S4 to the PWM circuit 27 via the insulation circuit 26. The stop signal S4 is a signal for stopping the switching operation of the switching circuit 20 and protecting the switching element Q3 from overheating.
Next, the operation of the switching power supply device 100 having the above-described configuration will be described. Hereinafter, the operation of each case will be described in detail in three cases, i.e., overheat protection, output short-circuit protection, and output low-voltage protection.
(1) Overheat protection
The overheat protection is a protection function necessary to prevent thermal destruction of the switching element Q3 when the element is abnormally heated and becomes a high temperature. The operation of the overheat protection will be described with reference to the flowchart of fig. 3.
In fig. 3, when an abnormality occurs in the switching element Q3 (a1), the element generates heat and the temperature gradually rises (a2), and when the temperature of the switching element Q3 detected by the temperature measurement element K exceeds a threshold value, the overheat detection circuit 29 detects overheat and outputs a stop signal S4 (A3). The stop signal S4 is supplied to the PWM circuit 27 via the insulation circuit 26, and the PWM circuit 27 stops outputting the PWM signal upon receiving the stop signal S4(a 4). As a result, the switching element Q3 is turned off, and the switching circuit 20 stops the switching operation (a 5).
When the switching circuit 20 stops the switching operation, the voltage is not applied to the primary winding La of the isolation transformer 21, and therefore the voltages of the main winding Lb and the auxiliary winding Lb drop, and as a result, the output voltages of the 1 st rectifier circuit 22 and the 2 nd rectifier circuit 23, that is, the main winding voltage Va and the auxiliary winding voltage Vb, both drop (a 6). The main winding voltage Va and the auxiliary winding voltage Vb are detected by the 1 st voltage detection circuit 24 and the 2 nd voltage detection circuit 25, respectively, and the detection results are transmitted to the control unit 9. When both of the winding voltages Va and Vb fall below the threshold, the controller 9 detects this and starts a timer (a 7).
On the other hand, in the switching circuit 20, the switching operation is stopped, and the temperature of the switching element Q3 gradually decreases (a 8). Therefore, the detection temperature of the temperature measuring element K also decreases. Then, when the overheat detection circuit 29 detects that the temperature of the switching element Q3 falls below the threshold, the output of the stop signal S4 is stopped (a 9). Therefore, the stop signal S4 is no longer supplied to the PWM circuit 27, and the PWM circuit 27 restarts outputting the PWM signal (a 10). Accordingly, the switching element Q3 is turned on and off again, and the switching circuit 20 resumes the switching operation (a11), so that both the main winding voltage Va and the auxiliary winding voltage Vb gradually rise (a 12). When both winding voltages Va and Vb rise to or above the threshold value, control unit 9 detects this and stops the timer (a 13).
Fig. 4 is a timing chart showing a case where the main winding voltage Va and the auxiliary winding voltage Vb change at the time of overheat protection. In fig. 4, in order to easily understand which time (or period) steps a1 to a13 in fig. 3 correspond to, these steps are also described.
In fig. 4, Vm and Vn denote a main winding voltage Va and an auxiliary winding voltage Vb at normal time, respectively (the same applies to fig. 6 and 8 described later). When an abnormality occurs at time t1, the temperature of the switching element Q3 rises, and the overheat detection circuit 29 detects an overheat at time t2, the switching operation of the switching circuit 20 is stopped as described above. Therefore, both the main winding voltage Va and the auxiliary winding voltage Vb gradually decrease from the normal voltages Vm, Vn. Then, at time t3 when the main winding voltage Va becomes less than the threshold value V α (Va < V α) and the auxiliary winding voltage Vb becomes less than the threshold value V β (Vb < V β), the control unit 9 starts a timer. Note that, although the threshold V α and the threshold V β are in a relationship of V α > V β, V α may be equal to V β or V α < V β (the same applies to fig. 6 and 8 described later).
Thereafter, both the main winding voltage Va and the auxiliary winding voltage Vb continue to drop, and at time t4, the voltages Va and Vb become substantially zero (Va ≈ 0 and Vb ≈ 0). However, since the current is not supplied to the switching element Q3 and the temperature of the element continues to decrease after the switching operation is stopped at time t2, the switching circuit 20 restarts the switching operation when the overheat detection circuit 29 does not output the stop signal S4 at time t5 at which the temperature is equal to or lower than the threshold value. Therefore, both the main winding voltage Va and the auxiliary winding voltage Vb start to rise. Then, at time t6 when main winding voltage Va becomes equal to or higher than threshold value V α (Va ≧ V α) and auxiliary winding voltage Vb becomes equal to or higher than threshold value V β (Vb ≧ V β), control unit 9 stops the timer. Thereafter, the winding voltages Va and Vb continue to rise, and when the voltages Vm and Vn become normal at time t7, the circuit returns to the normal state.
Here, the time X from the start of the timer at time t3 to the stop of the timer at time t6 is, for example, 400 s. The value of X is set so that the temperature of the switching element Q3 decreases at this time X and the switching operation is resumed (time t5), that is, the abnormal state is recovered. The time X corresponds to "1 st time" in the present invention.
In this way, in the case of the overheat protection, when the switching element Q3 is in the overheat state, the overheat detection circuit 29 detects this and outputs the stop signal S4 for stopping the switching operation to the PWM circuit 27, whereby the overheat detection circuit 29 directly stops the operation of the switching circuit 20 without passing through the control unit 9. Since the switching operation is restarted within the fixed time period X after the switching operation is stopped, and the winding voltages Va and Vb rise, the control unit 9 determines that the overheat detection circuit 29 has performed the overheat protection by detecting this.
(2) Output short circuit protection
The output short-circuit protection is a protection function necessary for preventing circuit components from being burned due to an overcurrent when a short circuit occurs between the output terminals T5 and T6. The operation of the output short-circuit protection will be described with reference to the flowchart of fig. 5.
In fig. 5, when a short circuit occurs between the output terminals T5, T6 (B1), the output voltage V2 of the 2 nd converter 102 falls (B2). Therefore, the feedback circuit 28 feedback-controls the PWM circuit 27 to increase the duty ratio (B3). As a result, the PWM circuit 27 outputs the PWM signal of the maximum duty ratio (B4). However, since the output terminals T5 and T6 are in a short-circuited state, the output voltage of the 1 st rectifier circuit 22, that is, the main winding voltage Va does not rise but continues to fall even when the switching circuit 20 performs a switching operation at the maximum duty ratio (B5). On the other hand, since the auxiliary winding voltage Vb that is the output voltage of the 2 nd rectifier circuit 23 is not affected by the short circuit between the output terminals T5 and T6, the switching circuit 20 performs the switching operation at the maximum duty ratio, and the auxiliary winding voltage Vb that is the output voltage of the 2 nd rectifier circuit 23 continues to rise (B5). During this period, the voltage detection circuits 24 and 25 continuously detect the winding voltages Va and Vb.
Then, when the control unit 9 detects that the main winding voltage Va has dropped and becomes less than the threshold value and the auxiliary winding voltage Vb has risen and exceeds the threshold value based on the outputs of the voltage detection circuits 24 and 25, the control unit 9 starts a timer (B6). Then, when the predetermined time has elapsed, the controller 9 determines that the output is short-circuited, stops the timer (B7), and stops outputting the permission signal S2 (B8). Thereby, the PWM circuit 27 is in the non-operating state, and the switching circuit 20 stops the switching operation (B9).
Fig. 6 is a timing chart showing a case where the main winding voltage Va and the auxiliary winding voltage Vb change at the time of outputting the short-circuit protection. In fig. 6, in order to easily understand which time (or period) steps B1 to B9 in fig. 5 correspond to, these steps are also described.
In fig. 6, when an output short circuit occurs at time t1', main winding voltage Va decreases from normal voltage Vm, and auxiliary winding voltage Vb increases from normal voltage Vn. Then, at time t2' when the main winding voltage Va becomes less than the threshold V α and the auxiliary winding voltage Vb becomes equal to or greater than the threshold V γ, the control unit 9 starts a timer. Then, at time t3', the main winding voltage Va becomes substantially zero, and the auxiliary winding voltage Vb becomes the maximum voltage. When time t4' at which a fixed time Y has elapsed since the start of the timer is reached, control unit 9 determines that the output is short-circuited and stops the timer. Further, the output of the permission signal S2 from the control unit 9 is stopped, and the switching circuit 20 also stops the switching operation.
When the switching operation is stopped at time t4', the auxiliary winding voltage Vb decreases, but the short-circuit state continues, and therefore the main winding voltage Va does not change (Va ≈ 0). When time t5' is reached, auxiliary winding voltage Vb also becomes substantially zero (Vb ≈ 0). When the short-circuit state is released at time t6', the switching operation is resumed, and both the main winding voltage Va and the auxiliary winding voltage Vb rise.
Here, the time Y from the start of the timer at time t2 'to the stop of the timer at time t4' is, for example, 200ms, and is set to a value much smaller than the time X (400s) in fig. 4 (Y is lengthened for convenience in fig. 6, but Y < X is actually used). This is because it is necessary to determine an output short circuit as early as possible and to quickly stop the switching operation to protect the circuit components from an overcurrent. The time Y corresponds to "time 2" in the present invention.
In this way, when the short-circuit protection is output, the main winding voltage Va decreases while the auxiliary winding voltage Vb increases, and therefore the control unit 9 detects a change in these voltages and determines that the output is short-circuited. Then, the control unit 9 stops outputting the permission signal S2, and the switching circuit 20 stops operating.
(3) Output low voltage protection
The output low voltage protection is a protection function required to detect a failure when electric power is no longer transmitted to the output side due to an open failure of the switching element Q3, a failure of the PWM circuit 27, or the like. The operation of the output low voltage protection will be described with reference to the flowchart of fig. 7.
In fig. 7, when an abnormality occurs due to a failure of the switching element Q3 or the PWM circuit 27 or the like (C1), power is no longer transmitted from the primary side to the secondary side of the isolation transformer 21, and therefore both the main winding voltage Va and the auxiliary winding voltage Vb drop (C2). When the control unit 9 detects that both the winding voltages Va and Vb have dropped below the threshold value based on the outputs of the voltage detection circuits 24 and 25, the control unit 9 starts a timer (C3). Then, when a certain time has elapsed, the control section 9 determines that a low voltage is output, and stops the timer (C4), and also outputs a failure detection signal (C5). The failure detection signal is transmitted to an on-vehicle ECU not shown, and the on-vehicle ECU executes processing such as alarm and display.
Fig. 8 is a timing chart showing a case where the main winding voltage Va and the auxiliary winding voltage are changed at the time of outputting the low voltage protection. In fig. 8, in order to easily understand which time (or period) steps C1 to C5 in fig. 7 correspond to, these steps are also described.
In fig. 8, when an abnormality occurs at time t1 ″ and electric power is no longer transmitted to the output side, both the main winding voltage Va and the auxiliary winding voltage Vb gradually decrease from the voltages Vm and Vn at the normal time. Then, at time t2 ″ when the main winding voltage Va becomes less than the threshold value V α (Va < V α) and the auxiliary winding voltage Vb becomes less than the threshold value V β (Vb < V β), the control unit 9 starts a timer.
Thereafter, both the main winding voltage Va and the auxiliary winding voltage Vb continue to drop, and at time t3 ″, the voltages Va and Vb become substantially zero (Va ≈ 0 and Vb ≈ 0). When time t4 ″ at which a fixed time Z has elapsed since the start of the timer is reached, control unit 9 determines that a low voltage is to be output, stops the timer, and outputs a failure detection signal. When the time elapses and the failure of the switching element Q3 or the like is resolved at time t5 ″, the switching operation is resumed, and both the main winding voltage Va and the auxiliary winding voltage Vb rise.
Here, time Z from the start of the timer at time t2 "to the stop of the timer at time t4" is set to a time longer than time X in fig. 4 (Y < X < Z). This is because, in the case of the overheat protection of fig. 4, since the temperature of the switching element Q3 naturally drops after the switching operation is stopped and the switching operation is automatically restarted, it is not necessary to set the time X to a long time, whereas in the case of the output low voltage protection of fig. 8, the switching operation is not restarted unless the failure is resolved, and therefore a certain long time Z is required to determine the output low voltage. The time Z corresponds to "time 3" in the present invention.
Therefore, when comparing the overheat protection and the output low-voltage protection, the same thing is that both the main winding voltage Va and the auxiliary winding voltage Vb are decreased due to an abnormality, but the difference between the two is that the switching operation is restarted (resumed) within a certain time X in the case of the overheat protection, whereas the switching operation is not restarted (resumed) within a certain time Z in the case of the output low-voltage protection.
In this way, when the low voltage protection is output, since the main winding voltage Va and the auxiliary winding voltage Vb both decrease and this state continues for a certain time, the control unit 9 detects a change in these voltages, determines that the output is a low voltage, and outputs a failure detection signal.
Fig. 9 shows the relationship between the circuit state, the protection function, and the winding voltage in the switching power supply device 100. If the circuit is in a normal state, both the main winding voltage Va and the auxiliary winding voltage Vb maintain a high voltage (voltages Vm, Vn in normal times in fig. 4 and the like). When the switching element Q3 is overheated, the overheat protection function (1) functions to stop the switching operation and lower the winding voltages Va and Vb, but automatically recovers (resumes the switching operation) for a certain period of time. When a short circuit occurs between the output terminals T5 and T6, the main winding voltage Va decreases, but the auxiliary winding voltage Vb increases, the output short-circuit protection function (2) is activated, and the switching operation is stopped. In this case, the recovery is not automatically performed for a certain time. When the output voltage V2 drops, the main winding voltage Va and the auxiliary winding voltage Vb both drop, and the output low voltage protection function (3) functions to detect a fault. In this case, the recovery is not automatically performed for a certain period of time.
As can be seen from fig. 9, the overheat protection function (1) and the output short-circuit protection function (2) can be distinguished from each other by the difference in the change in the auxiliary winding voltage Vb. In addition, the output short-circuit protection function (2) and the output low-voltage protection function (3) can be distinguished from each other by the difference in the change in the auxiliary winding voltage Vb. On the other hand, the overheat protection function (1) and the output low-voltage protection function (3) cannot be distinguished only by the winding voltages Va and Vb, but can be distinguished by the presence or absence of automatic recovery within a certain period of time.
Fig. 10 shows a comparative example of the present invention. In the drawings, the same components as those in fig. 2 are denoted by the same reference numerals. In fig. 10, in addition to the configuration of fig. 2, an interface circuit 30 provided between the overheat detection circuit 29 and the control unit 9 and an overcurrent detection circuit 31 provided between the 1 st rectifier circuit 22 and the output terminal T5 are provided. The interface circuit 30 is a circuit for electrically isolating the output signal of the overheat detection circuit 29 and inputting the signal to the control unit 9. The overcurrent detection circuit 31 is a circuit that detects an overcurrent that flows when a short circuit occurs between the output terminals T5, T6. The output of the overcurrent detection circuit 31 is input to the control unit 9.
In the case of the configuration shown in fig. 10, the control unit 9 determines that the output voltage is low based on the output (main winding voltage) of the 1 st voltage detection circuit 24 and the output (auxiliary winding voltage) of the 2 nd voltage detection circuit 25. This is not different from the case of fig. 2. However, in the overheat protection, while in fig. 2 the overheat detection circuit 29 itself outputs a stop signal to stop the switching operation when the switching element Q3 is overheated, in fig. 10 the control unit 9 determines whether or not the switching element Q3 is overheated based on the output signal of the overheat detection circuit 29, and when it is determined that the switching element Q is overheated, stops outputting the permission signal S2 to stop the switching operation. While in fig. 2 the control unit 9 determines the presence or absence of an output short circuit based on the output of the 1 st voltage detection circuit 24 (main winding voltage Va) and the output of the 2 nd voltage detection circuit 25 (main winding voltage Vb), in fig. 10 the control unit 9 determines the presence or absence of an output short circuit based on the output signal of the overcurrent detection circuit 31.
As is clear from comparison between fig. 2 and 10, in the case of fig. 10, since the interface circuit 30 and the overcurrent detection circuit 31 are provided, the circuit configuration becomes more complicated than that of fig. 2. On the other hand, in the case of fig. 2, since the overheat detection circuit 29 outputs the stop signal S4 to stop the switching operation, the interface circuit 30 of fig. 10 is not necessary, and since the presence or absence of the output short circuit can be determined from the outputs of the 1 st voltage detection circuit 24 and the 2 nd voltage detection circuit 25, the overcurrent detection circuit 31 of fig. 10 is not necessary. In the case of fig. 10, the control unit 9 determines whether or not the switching element Q3 has overheated, and therefore the load on the control unit 9 increases, whereas in the case of fig. 2, the control unit 9 does not need to determine whether or not there is overheating, and therefore the load on the control unit 9 is reduced.
As described above, according to the switching power supply device 100 of the present embodiment, when the switching element Q3 is in the overheat state, the overheat protection can be performed by stopping the switching operation of the switching circuit 20 without passing through the control unit 9 by the stop signal S4 output from the overheat detection circuit 29. The control unit 9 can determine that the output of the 2 nd converter 102 is short-circuited or the voltage drops by comparing the change in the detection voltage (main winding voltage Va) of the 1 st voltage detection circuit 24 and the change in the detection voltage (auxiliary winding voltage Vb) of the 2 nd voltage detection circuit 25. Therefore, the interface circuit 30 (fig. 10) is not required between the overheat detection circuit 29 and the control unit 9, and the overcurrent detection circuit 31 (fig. 10) for detecting an output short circuit is not required, so that the circuit configuration is simplified and the load on the control unit 9 is reduced. In addition, although the circuit configuration is simple, protection can be accurately performed in accordance with the type of abnormality as shown in fig. 9.
In the present invention, in addition to the above-described embodiments, various embodiments described below can be adopted.
In the above embodiment, various protection functions in the 2 nd converter 102 have been described, but the 1 st converter 101 may be provided with the same configuration as that in fig. 1 and 2, or the two converters 101 and 102 may be provided with the same configuration. The present invention is not limited to the switching power supply device 100 having the 1 st converter 101 and the 2 nd converter 102, and can be applied to a switching power supply device having only one converter or a switching power supply device having three or more converters.
In the above-described embodiment, the switching power supply device 100 having all the functions (1) to (3) of fig. 9 is exemplified, but the present invention is not limited thereto. For example, the present invention can also be applied to a switching power supply device having only an overheat protection function (1) and an output short-circuit protection function (2), or a switching power supply device having only an overheat protection function (1) and an output low-voltage protection function (3). The present invention can also be applied to a switching power supply device having only an output short-circuit protection function (2) and an output low-voltage protection function (3). In this case, the overheat detection circuit 29 and the temperature measuring element K are not required.
In the above embodiment, in the operation of the output short-circuit protection shown in fig. 5, when the output short circuit is detected (determined), the output permission signal S2 is immediately stopped to stop the switching operation (B7 to B9), but the control unit 9 may count the number of times the short circuit is detected, and when the number of times reaches the predetermined number N (N ≧ 2), the control unit 9 stops the output permission signal S2 to stop the switching operation.
In the above embodiment, the control unit 9 stops the switching operation by stopping the output of the permission signal S2 when outputting the short circuit, but may stop the switching operation by outputting a prohibition signal different from the permission signal S2 when outputting the short circuit.
In the above embodiment, the switching operation is stopped by supplying the stop signal S4 output from the overheat detection circuit 29 to the PWM circuit 27, but the switching operation may be stopped by supplying the stop signal S4 to the switching circuit 20. Similarly, the permission signal S2 (or the prohibition signal) output from the control unit 9 may be supplied to the switch circuit 20.
In the above embodiment, the 1 st converter 101 and the 2 nd converter 102 are both step-down DC-DC converters, but the converters 101 and 102 may be step-up DC-DC converters. One of the converters 101 and 102 may be a step-down DC-DC converter, and the other may be a step-up DC-DC converter.
In the above embodiment, the 1 st converter 101 and the 2 nd converter 102 are both insulated DC-DC converters, but the converters 101 and 102 may be non-insulated DC-DC converters.
In the above embodiment, the PWM circuit 27 is exemplified as the drive circuit for driving the switch circuit 20, but a drive circuit for driving the switch circuit 20 by a method other than PWM may be provided.
In the above-described embodiment, the switching power supply device 100 mounted on a vehicle is exemplified, but the switching power supply device of the present invention can be applied to applications other than those mounted on a vehicle.
Claims (9)
1. A switching power supply device includes:
a converter that switches an input dc voltage and converts the dc voltage into a dc voltage having a predetermined voltage value; and
a control unit for controlling the operation of the converter,
the converter includes:
a switching circuit having a switching element for switching the dc voltage by an on/off operation of the switching element;
a drive circuit that drives the switch circuit;
a rectifier circuit that rectifies a voltage that is switched by the switching circuit and converted into an alternating current; and
an insulation transformer provided between the switching circuit and the rectifying circuit and having a primary winding connected to the switching circuit and a secondary winding connected to the rectifying circuit,
it is characterized in that the preparation method is characterized in that,
the secondary winding of the insulation transformer is composed of a main winding and an auxiliary winding,
the rectifier circuit is composed of a1 st rectifier circuit and a2 nd rectifier circuit, the 1 st rectifier circuit is arranged between the main winding and the output terminal of the converter, the 2 nd rectifier circuit is connected with the auxiliary winding,
the switching power supply device further includes:
a1 st voltage detection circuit that detects an output voltage of the 1 st rectifier circuit;
a2 nd voltage detection circuit that detects an output voltage of the 2 nd rectifier circuit;
an overheat detection circuit that detects an overheat state of the switching element; and
a feedback circuit that feedback-controls the drive circuit so that an output voltage of the converter becomes a target value,
the overheat detection circuit outputs a stop signal for stopping the switching operation of the switching circuit to perform overheat protection when the temperature of the switching element exceeds a threshold value,
the control unit determines whether the output of the converter is short-circuited or the output of the converter is low voltage, based on a result of comparing the change in the voltage detected by the 1 st voltage detection circuit with the change in the voltage detected by the 2 nd voltage detection circuit, and executes control for outputting short-circuit protection or low-voltage protection based on the determination result.
2. Switching power supply unit according to claim 1,
when the voltage detected by the 1 st voltage detection circuit is lower than the normal voltage and the voltage detected by the 2 nd voltage detection circuit continues to be lower than the normal voltage for a predetermined time and before the lapse of a predetermined 1 st time, the control unit determines that the overheat detection circuit has performed the overheat protection,
when the voltage detected by the 1 st voltage detection circuit is lower than the normal voltage and the voltage detected by the 2 nd voltage detection circuit is higher than the normal voltage for a predetermined 2 nd time, the control unit determines that the output of the converter is short-circuited and executes control for outputting short-circuit protection,
when the voltage detected by the 1 st voltage detection circuit is lower than the voltage at the normal time and the state in which the voltage detected by the 2 nd voltage detection circuit is lower than the voltage at the normal time continues for the 3 rd time longer than the 1 st time, the control unit determines that the output of the converter is a low voltage and executes control for outputting low-voltage protection.
3. Switching power supply unit according to claim 1,
when the voltage detected by the 1 st voltage detection circuit is lower than the normal voltage and the voltage detected by the 2 nd voltage detection circuit continues to be lower than the normal voltage for a predetermined time and before the lapse of a predetermined 1 st time, the control unit determines that the overheat detection circuit has performed the overheat protection,
when the voltage detected by the 1 st voltage detection circuit is lower than the normal voltage and the voltage detected by the 2 nd voltage detection circuit is higher than the normal voltage for a predetermined 2 nd time, the control unit determines that the output of the converter is short-circuited and executes control for outputting short-circuit protection.
4. Switching power supply unit according to claim 1,
when the voltage detected by the 1 st voltage detection circuit is lower than the normal voltage and the voltage detected by the 2 nd voltage detection circuit continues to be lower than the normal voltage for a predetermined time and before the lapse of a predetermined 1 st time, the control unit determines that the overheat detection circuit has performed the overheat protection,
when the voltage detected by the 1 st voltage detection circuit is lower than the voltage at the normal time and the state in which the voltage detected by the 2 nd voltage detection circuit is lower than the voltage at the normal time continues for the 3 rd time longer than the 1 st time, the control unit determines that the output of the converter is a low voltage and executes control for outputting low-voltage protection.
5. A switching power supply device includes:
a converter that switches an input dc voltage and converts the dc voltage into a dc voltage having a predetermined voltage value; and
a control unit for controlling the operation of the converter,
the converter includes:
a switching circuit having a switching element for switching the dc voltage by an on/off operation of the switching element;
a drive circuit that drives the switch circuit;
a rectifier circuit that rectifies a voltage that is switched by the switching circuit and converted into an alternating current; and
an insulation transformer provided between the switching circuit and the rectifying circuit and having a primary winding connected to the switching circuit and a secondary winding connected to the rectifying circuit,
it is characterized in that the preparation method is characterized in that,
the secondary winding of the insulation transformer is composed of a main winding and an auxiliary winding,
the rectifier circuit is composed of a1 st rectifier circuit and a2 nd rectifier circuit, the 1 st rectifier circuit is arranged between the main winding and the output terminal of the converter, the 2 nd rectifier circuit is connected with the auxiliary winding,
the switching power supply device further includes:
a1 st voltage detection circuit that detects an output voltage of the 1 st rectifier circuit;
a2 nd voltage detection circuit that detects an output voltage of the 2 nd rectifier circuit; and
a feedback circuit that feedback-controls the drive circuit so that an output voltage of the converter becomes a target value,
the control unit determines whether the output of the converter is short-circuited or the output of the converter is low voltage, based on a result of comparing the change in the voltage detected by the 1 st voltage detection circuit with the change in the voltage detected by the 2 nd voltage detection circuit, and executes control for outputting short-circuit protection or low-voltage protection based on the determination result.
6. Switching power supply unit according to claim 5,
when the voltage detected by the 1 st voltage detection circuit is lower than the normal voltage and the voltage detected by the 2 nd voltage detection circuit is higher than the normal voltage for a predetermined time, the control unit determines that the output of the converter is short-circuited and executes control for outputting short-circuit protection,
when the voltage detected by the 1 st voltage detection circuit is lower than the normal voltage and the voltage detected by the 2 nd voltage detection circuit is lower than the normal voltage for a time longer than the predetermined time, the control unit determines that the output of the converter is a low voltage and executes control for outputting low-voltage protection.
7. The switching power supply device according to any one of claims 1 to 3, 5, and 6,
the control unit outputs a permission signal when the switching circuit is permitted to perform a switching operation, and stops the permission signal or outputs a prohibition signal different from the permission signal when it is determined that the output of the converter is short-circuited, thereby stopping the switching operation of the switching circuit and performing output short-circuit protection.
8. The switching power supply device according to claim 7,
the control unit stops the permission signal or outputs the prohibition signal when the number of times of short-circuiting of the output of the converter reaches a predetermined number of times.
9. The switching power supply device according to any one of claims 1, 2, 4 to 6,
the control unit outputs a failure detection signal as control for the output low voltage protection.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2019-137303 | 2019-07-25 | ||
| JP2019137303A JP7198169B2 (en) | 2019-07-25 | 2019-07-25 | switching power supply |
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| CN112311240A true CN112311240A (en) | 2021-02-02 |
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| CN202010703017.9A Pending CN112311240A (en) | 2019-07-25 | 2020-07-21 | Switching power supply device |
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Family Cites Families (3)
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| JP2000092744A (en) * | 1998-09-11 | 2000-03-31 | Canon Inc | Power supply device and its control method, and image- recording device and its control method |
| JP2003153530A (en) * | 2001-11-14 | 2003-05-23 | Nissan Motor Co Ltd | Switching power supply apparatus |
| JP2007174890A (en) * | 2005-11-28 | 2007-07-05 | Matsushita Electric Ind Co Ltd | Switching power supply and semiconductor device used for it |
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| JP2021022995A (en) | 2021-02-18 |
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