CN109314465B - Switching power supply device - Google Patents
Switching power supply device Download PDFInfo
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- CN109314465B CN109314465B CN201680086428.XA CN201680086428A CN109314465B CN 109314465 B CN109314465 B CN 109314465B CN 201680086428 A CN201680086428 A CN 201680086428A CN 109314465 B CN109314465 B CN 109314465B
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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
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Abstract
Provided is a switching power supply device capable of stabilizing operation even if the output voltage greatly changes. A switching power supply device (1) which transmits input power (Vi) applied to a primary coil (P1) to a secondary coil (S) and returns power from the secondary coil (S) to an auxiliary coil (P2) to generate a drive power supply (Vcc) of a primary-side control IC (10) which controls on/off of a switching element (Q1) from the auxiliary coil (P2), wherein the switching power supply device (1) comprises: a step-down circuit (30) that is turned on/off in accordance with the voltage of the auxiliary coil (P2), and that, when turned on, supplies a constant voltage, which is obtained by reducing the voltage of the auxiliary coil (P2), to the primary-side control IC (10) as a drive power supply (Vcc); a step-down operation detection circuit (40) that detects the operation of the step-down circuit (30); and a condition changing circuit (overcurrent detection condition correction circuit (50), gate resistance changing circuit (60)) which changes the operating condition of the primary side by using a gate pulse for driving the switching element (Q1) according to the operation of the voltage reducing circuit.
Description
Technical Field
The present invention relates to a switching power supply device in which an output voltage is variable in a wide range.
Background
In recent years, as a new USB operation mode, a standard such as USB power delivery (hereinafter, referred to as USBPD) has been established. The USBPD communicates with the electrical devices and when the negotiation is established, the output voltage can be varied from 5V to a maximum of 20V.
In general, in a switching power supply device, an auxiliary coil whose voltage depends on a turn ratio with respect to a secondary coil is used as a driving power supply for a primary-side control IC. Therefore, in order to operate the primary side control IC in accordance with a wide range of output voltages, it is necessary to increase the turn ratio of the auxiliary coil to the secondary side coil, and to make the driving power supply equal to or higher than the operating voltage of the primary side control IC even if the output voltage is low. On the other hand, when the output voltage is high, the voltage of the auxiliary winding reaches the withstand voltage of the primary-side control IC in this state, and therefore, a step-down device is provided to reduce the voltage of the auxiliary winding to the withstand voltage of the primary-side control IC or less (for example, see patent document 1).
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 2004-88839
Disclosure of Invention
Problems to be solved by the invention
However, in the USBPD, as a standard, the maximum value (3A or 5A) of the output current is set. Therefore, when the switching power supply device is designed at 20V/3A (60W), there are problems as follows: when 5V is output, the secondary side power is low, and an excessive output current flows until the primary side overcurrent protection is performed.
The present invention has been made to solve the above problems of the prior art, and an object of the present invention is to provide a switching power supply device capable of stabilizing operation even if an output voltage greatly changes.
Means for solving the problems
A switching power supply device according to the present invention is a switching power supply device that transmits input power applied to a primary coil of a transformer to a secondary coil of the transformer by on/off controlling a switching element connected to the primary coil, and that generates a drive power supply for a primary-side control circuit that on/off controls the switching element from an auxiliary coil of the transformer by transmitting power from the secondary coil to the auxiliary coil, the switching power supply device including: a voltage reduction circuit that is turned on/off in accordance with the voltage of the auxiliary coil, and supplies a constant voltage obtained by reducing the voltage of the auxiliary coil to the primary control circuit as the drive power supply when the voltage reduction circuit is turned on; a step-down detection circuit that detects an operation of the step-down circuit; and a condition changing circuit that changes an operation condition on the primary side using a drive signal for driving the switching element in accordance with an operation of the voltage-reducing circuit.
In the switching power supply device according to the present invention, the constant voltage supplied to the primary side control circuit by the voltage reduction circuit may be higher than a starting voltage of the primary side control circuit.
In the switching power supply device according to the present invention, the step-down detection circuit may detect on/off of the step-down circuit, and the condition change circuit may switch the operating condition in accordance with the on/off of the step-down circuit.
In the switching power supply device according to the present invention, the step-down circuit may include a zener diode that is turned on/off in accordance with a voltage of the auxiliary winding, and the step-down detection circuit may detect on/off of the step-down circuit based on/off of the zener diode.
In the switching power supply device according to the present invention, the primary-side control circuit may have an overcurrent detection function of detecting an overcurrent based on a value of a current flowing through the switching element and input from an overcurrent detection input terminal, and the condition change circuit may switch an input condition of the current value to the overcurrent detection input terminal in accordance with on/off of the step-down circuit.
In the switching power supply device according to the present invention, the condition changing circuit may switch the driving condition of the switching element based on the driving signal in accordance with on/off of the step-down circuit.
In the switching power supply device according to the present invention, the step-down detection circuit may detect an operating condition of the step-down circuit, and the condition change circuit may change the operating condition in accordance with the operating condition of the step-down circuit.
In the switching power supply device according to the present invention, the step-down circuit may include a transistor, a voltage between main terminals of the transistor, which is a step-down amount, may be adjusted in accordance with a voltage of the auxiliary winding, and the step-down detection circuit may detect the voltage between the main terminals of the transistor as an operation state of the step-down circuit.
In the switching power supply device according to the present invention, the primary-side control circuit may have an overcurrent detection function of detecting an overcurrent based on a value of a current flowing through the switching element, the current being input from an overcurrent detection input terminal, and the condition change circuit may change an input condition of the current value being input to the overcurrent detection input terminal in accordance with an operating state of the step-down circuit.
In the switching power supply device according to the present invention, the condition changing circuit may change a driving condition of the switching element based on the driving signal in accordance with an operating state of the step-down circuit.
Effects of the invention
According to the present invention, the operation condition of the primary side can be changed in accordance with the setting of the output voltage, and the effect of stabilizing the operation when the output voltage greatly changes is achieved.
Drawings
Fig. 1 is a circuit configuration diagram showing a circuit configuration of embodiment 1 of the switching power supply device of the present invention.
Fig. 2 is a diagram for explaining an overcurrent protection operation of the primary-side control IC shown in fig. 1.
Fig. 3 is a circuit configuration diagram showing a circuit configuration of embodiment 2 of the switching power supply device of the present invention.
Detailed Description
Next, embodiments of the present invention will be described in detail with reference to the drawings.
(embodiment 1)
The switching power supply device 1 according to embodiment 1 is a Converter (Converter) for a USB power delivery (hereinafter, referred to as USBPD), and converts an input voltage Vi into an output voltage Vo of 5V or 20V and outputs the converted voltage Vo. Referring to fig. 1, a switching power supply device 1 includes: smoothing capacitors C1 and C21, a transformer T, a primary-side control IC10, a secondary-side circuit 20, a switching element Q1, a transistor Q2, a switching element Q3, Q4, Q5, diodes D1, D2, D3, D21, a zener diode ZD1, resistors R1 to R10, and a capacitor C2.
The primary-side control IC10 incorporates a control circuit for performing switching control of a switching element Q1 formed of a MOSFET (Metal Oxide semiconductor field Effect Transistor) or the like, and has a Gate (Gate drive output) terminal, a Cs (overcurrent detection input) terminal, a Vcc (power supply voltage input) terminal, and a GND (ground) terminal.
A transformer T for supplying power from a primary side (input side) to a secondary side (load side) is configured by a primary coil P1, an auxiliary coil P2, and a secondary coil S. One end of the primary coil P1 is connected to the positive terminal of the input voltage Vi, and the other end of the primary coil P is connected to the drain of the switching element Q1. The source of the switching element Q1 is connected to the negative terminal (GND terminal) of the input voltage Vi via a resistor R9. The Gate terminal of the primary-side control IC10 is connected to the Gate of the switching element Q1 via resistors R1 and R2 connected in series. Thus, the primary-side control IC10 controls the switching element Q1 to be turned on and off by the Gate pulse output from the Gate terminal, and transmits the power applied to the primary winding P1 of the transformer T to the secondary winding S of the transformer T. Further, a resistor R1 is connected in parallel with the diode D1. The diode D1 is connected in a direction to discharge electric charge from the switching element Q1, and the off time of the switching element Q is set to be shorter than the on time.
A smoothing capacitor C21 is connected between both terminals of the secondary winding S of the transformer T via a diode D21. The voltage induced in the secondary winding S of the transformer T is rectified and smoothed by the diode D21 and the smoothing capacitor C21, and the inter-terminal voltage of the smoothing capacitor C21 is input to the secondary-side circuit 20.
The secondary-side circuit 20 is composed of the following circuits: an SW (switch) circuit that switches the setting of the output voltage Vo to either 5V or 20V; a CV (constant voltage) circuit that stabilizes the output voltage Vo; and an FB (feedback) circuit that feeds back a Feedback (FB) signal corresponding to the output voltage Vo set by the SW circuit to the primary-side control IC 10. The primary side control IC10 controls the duty ratio of the switching element Q1 based on the FB signal from the secondary side circuit 20, thereby controlling the amount of power supplied to the secondary side.
A smoothing capacitor C1 is connected between both terminals of the auxiliary winding P2 of the transformer T via a diode D3. The reactor L1 interposed between the auxiliary coil P2 and the diode D3 suppresses surgeThe element of (1). Instead of the reactor L1, a resistor may be used. The voltage V of the smoothing capacitor C1C1The voltage-reducing circuit 30 is configured by a transistor Q2, a resistor R3, and a zener diode ZD1 as a power supply voltage for IC supplied to the Vcc terminal of the primary side control IC10 via the voltage-reducing circuit 30 and a diode D2.
The positive terminal of the smoothing capacitor C1 is connected to the Vcc terminal of the primary-side control IC10 via the transistor Q2 and the diode D2, and the negative terminal of the smoothing capacitor C1 is connected to the GND terminal of the primary-side control IC 10. The transistor Q2 is an NPN type, and the transistor Q2 has a collector connected to the positive terminal of the smoothing capacitor C1 and an emitter connected to the anode of the diode D2. The cathode of the diode D2 is connected to the Cs terminal of the primary-side control IC 10.
Further, a resistor R3, a zener diode ZD1, and a resistor R4 are connected in series between the positive electrode terminal and the negative electrode terminal of the smoothing capacitor C1. The base of the transistor Q2 is connected to a connection point between the resistor R3 and the cathode of the zener diode ZD1, and the anode of the zener diode ZD1 is connected to the GND terminal of the primary-side control IC10 via the resistor R4.
A connection point between the source terminal of the switching element Q1 and the resistor R9 is connected to a Cs (overcurrent detection input) terminal of the primary-side control IC10 via an RC filter including a resistor R8 and a capacitor C2 and a resistor R7.
Further, a resistor R5 and a switching element Q4 are connected in series between the Gate terminal and the Cs terminal of the primary-side control IC 10. The switching element Q4 is an N-type MOSFET, and the switching element Q4 has a drain connected to the Gate terminal of the primary-side control IC10 via a resistor R5 and a source connected to the Cs terminal of the primary-side control IC 10. The gate of the switching element Q4 is connected to the Vcc terminal of the primary-side control IC10 via a resistor R6, and is connected to the GND terminal of the primary-side control IC10 via a switching element Q3.
The switching element Q3 is formed of an NPN transistor, and the switching element Q3 has a collector connected to the gate of the switching element Q4, an emitter connected to the GND terminal of the primary-side control IC10, and a base connected to a connection point between the anode of the zener diode ZD1 and the resistor R4.
The voltage-reducing circuit 30 is set to be off when the output voltage Vo is set to 5V and to be on when the output voltage Vo is set to 20V. The operating voltage of the step-down circuit 30 is defined by a zener voltage Vz of the zener diode ZD1 and a base-emitter voltage Vbe of the transistor Q3Q3It was determined that when the output voltage Vo was set to 20V (high output voltage Vo), the voltage V of the smoothing capacitor C1 wasC1Becomes (Vz + Vbe)Q3) The above. Thus, the step-down circuit 30 is turned on from Vz + VbeQ3Start (base-emitter voltage Vbe of transistor Q2Q2Forward voltage Vf of + diode D2D2) The constant voltage after the drop is applied to the Vcc terminal of the primary-side control IC 10. The (Vz + Vbe)Q3)-(VbeQ2+VfD2) The voltage is set to a value higher than the starting voltage of the primary control IC10 and lower than the withstand voltage.
The voltage V of the smoothing capacitor C1 was set to 5V (low output voltage Vo) as the output voltage VoC1Less than Vz + VbeQ3. Thereby, the step-down circuit 30 (zener diode ZD1) is turned off, the transistor Q2 is self-biased, and the secondary voltage V is applied to the Vcc terminal of the primary control IC10C1Start (Vbe)Q2+VfD2) The dropped voltage.
The switching element Q3 and the resistor R4 function as a step-down operation detection circuit 40 that detects on/off of the step-down circuit 30. That is, the transistor Q3 is turned on in a state where the output voltage Vo is set to 20V (high output voltage Vo) and the voltage-reducing circuit 30 (zener diode ZD1) is turned on, and the transistor Q3 is turned off in a state where the output voltage Vo is set to 5V (low output voltage Vo) and the voltage-reducing circuit 30 (zener diode ZD1) is turned off.
The switching element Q4 and the resistors R5, R6, and R7 function as an overcurrent detection condition correction circuit 50 that corrects an overcurrent detection condition. When the transistor Q3 is turned on, that is, when the step-down operation detection circuit 40 detects the on state of the step-down circuit 30, the switching element Q4 is turned off. Thus, the resistor R9 is used as the voltage signal VIdThe drain current Id of the detected switching element Q2 is input to the primary-side control IC via the RC filter for preventing surge error detection10 Cs terminal. The primary control IC10 has an overcurrent protection function, and as shown in fig. 2 (a), it is provided for VIdAnd an overcurrent threshold VthMaking a comparison when VIdOver-current threshold VthAt this time, an overcurrent protection operation for limiting the power supplied to the secondary side is performed.
When the transistor Q3 is turned off, that is, when the step-down operation detection circuit 40 detects the off state of the step-down circuit 30, a voltage is applied to the gate of the switching element Q4 via the resistor R6, and the switching element Q4 is turned on. As a result, the voltage at the Cs terminal is biased by the Gate pulse output from the Gate terminal of the primary-side control IC10, and the voltage signal V detected by the resistor R9 is shown in fig. 2 (b)IdAt a voltage VupThe amount of (c) increases. Then, in the primary control IC10, V after rising is subjected toIdAnd an overcurrent threshold VthComparing, when V is increasedIdOver-current threshold VthAt this time, an overcurrent protection operation for limiting the power supplied to the secondary side is performed. Voltage signal VIdRising voltage VupDepending on the voltage division ratio between the resistor R5 and the resistor R7, the overcurrent protection operation can be performed under substantially the same condition even when the output voltage Vo is switched in the primary-side control IC 10.
Further, a switching element Q5 and a resistor R10 connected in series are connected in parallel to the resistors R1 and R2 as gate resistances (gate resistances). The switching element Q5 is a P-type MOSFET, and the switching element Q5 has a source connected to the Gate terminal of the primary-side control IC10, a drain connected to the Gate of the switching element Q1 via a resistor R10, and a Gate connected to a connection point between the resistor R5 and the drain of the switching element Q4.
The switching element Q5 and the resistor R10 function as a gate resistance changing circuit 60 that switches a gate resistance. The switching element Q5 is turned on when the switching element Q4 is turned on, and is turned off when the switching element Q4 is turned off. Thus, when the output voltage Vo is set to 5V (low output voltage Vo), the switching element Q4 is turned on, the resistors R1 and R2 are connected to the parallel resistor (resistor R10), and the switching speed of the switching element Q1 increases.
That is, the gate resistance formed by the resistors R1 and R2 is a gate resistance in which the output voltage Vo corresponds to 20V (high output voltage Vo), and when the output voltage Vo is 5V (low output voltage Vo), the switching speed is slow, and the EMI is over-designed. Therefore, when the output voltage Vo is 5V (low output voltage Vo), the gate resistance is decreased to increase the switching speed, thereby reducing the loss.
(embodiment 2)
Referring to fig. 3, the switching power supply device 1a according to embodiment 2 is configured to be able to set the output voltage Vo to an arbitrary voltage of 5V to 20V by the secondary side circuit 20a, convert the input voltage Vi into the output voltage Vo set to an arbitrary voltage of 5V to 20V, and output the output voltage Vo.
In the switching power supply device 1a, a step-down operation state detection circuit 70 that detects an operation state of the step-down circuit 30 is provided in place of the step-down operation detection circuit 40 that detects on/off of the step-down circuit 30. The step-down operation state detection circuit 70 is composed of a differential amplifier OP1, and the non-inverting input terminal of the differential amplifier OP1 is connected to the collector of the transistor Q2, and the inverting input terminal thereof is connected to the emitter of the transistor Q2. Thus, the collector-emitter voltage Vce of the transistor Q2 is output from the output terminal of the differential amplifier OP1Q2I.e., the step-down amount of the step-down circuit 30, as a voltage signal.
In the overcurrent detection condition correction circuit 50a, a current source CC1 that flows a current corresponding to the output level of the differential amplifier OP1 is provided in place of the switching element Q4. The current source CC1 supplies a current corresponding to the output level of the differential amplifier OP1 to the connection point of the Cs terminal and the resistor R7 using the Gate pulse output from the Gate terminal of the primary-side control IC 10. Collector-emitter voltage Vce of transistor Q2Q2The smaller the output level of the differential amplifier OP1, the larger the current source CC1 supplies to the connection point of the Cs terminal and the resistor R7. Thus, the voltage signal V detected by the resistor R9IdRises in accordance with the set output voltage Vo.
In the primary control IC10, the V after rising is processedIdAnd an overcurrent threshold VthComparing, when V is increasedIdOver-current threshold VthAt this time, an overcurrent protection operation for limiting the power supplied to the secondary side is performed. Voltage signal VIdRising voltage VupDepending on the current value supplied from the current source CC1, the overcurrent protection operation can be performed under substantially the same condition even if the output voltage Vo is changed in the primary-side control IC 10.
In the gate resistance changing circuit 60a, a current source CC2 for flowing a current corresponding to the output level of the differential amplifier OP1 is provided in place of the switching element Q5. The current source CC2 supplies a current corresponding to the output level of the differential amplifier OP1 to the Gate of the switching element Q1 via the resistor R10 using a Gate pulse output from the Gate terminal of the primary-side control IC 10. Collector-emitter voltage Vce of transistor Q2Q2The smaller the output level of the differential amplifier OP1, the more the current source CC2 supplies a larger current to the gate of the switching element Q1 via the resistor R10. Accordingly, the switching speed of the switching element Q1 increases as the output voltage Vo decreases. Therefore, the driving condition of the switching element can be adjusted to be optimal according to the output voltage Vo.
As described above, according to the present embodiment, the switching power supply device 1, 1a, which transmits the input power Vi applied to the primary coil P1 to the secondary coil S and returns the power from the secondary coil S to the auxiliary coil P2 by on/off controlling the switching element Q1 connected to the primary coil P1 of the transformer T, generates the drive power supply Vcc of the primary side control circuit (primary side control IC 10) which on/off controls the switching element Q1 from the auxiliary coil P2, includes: a step-down circuit 30 that is turned on/off in accordance with the voltage of the auxiliary winding P2, and supplies a constant voltage obtained by reducing the voltage of the auxiliary winding P2 to the primary control circuit (primary control IC 10) as the drive power supply Vcc when turned on; a step-down detection circuit (step-down operation detection circuit 40, step-down operation status detection circuit 70) for detecting the operation of the step-down circuit 30; and a condition changing circuit (overcurrent detection condition correcting circuit 50, 50a, gate resistance changing circuit 60, 60a) that changes the operating condition of the primary side by using a drive signal (gate pulse) for driving the switching element Q1 in accordance with the operation of the step-down circuit.
According to this configuration, the operation condition on the primary side is changed in accordance with the setting of the output voltage Vo, and the operation can be stabilized even if the output voltage Vo greatly changes.
In the present embodiment, the constant voltage supplied from the voltage-reducing circuit 30 to the primary-side control circuit (primary-side control IC 10) is set to be higher than the start voltage of the primary-side control circuit (primary-side control IC 10).
With this configuration, even if the output voltage Vo greatly changes, the primary control circuit (the primary control IC 10) can be operated stably.
Further, according to the present embodiment, the step-down detection circuit (step-down operation detection circuit 40) detects the on/off of the step-down circuit 30, and the condition change circuit (overcurrent detection condition correction circuit 50, gate resistance change circuit 60) switches the operation condition in accordance with the on/off of the step-down circuit 30.
With this configuration, switching of the output voltage Vo can be detected on the primary side by turning on/off the voltage-reducing circuit 30.
Further, according to the present embodiment, the step-down circuit 30 includes the zener diode ZD1 that turns on/off in accordance with the voltage of the auxiliary winding P2, and the step-down detection circuit (step-down operation detection circuit 40) detects the turning on/off of the step-down circuit 30 in accordance with the turning on/off of the zener diode ZD 1.
According to this configuration, by detecting the current flowing through zener diode ZD1, the on/off of voltage step-down circuit 30 can be easily detected.
Further, according to the present embodiment, the primary side control circuit (the primary side control IC 10) has an overcurrent detection function of detecting an overcurrent based on a current value (drain current Id) flowing through the switching element Q1 inputted from the Cs terminal, and the condition changing circuit (the overcurrent detection condition correcting circuit 50) switches an input condition of inputting the current value (drain current Id) to the Cs terminal in accordance with on/off of the step-down circuit 30.
According to this configuration, even if the output voltage Vo is switched, the overcurrent protection operation can be stably performed.
Further, according to the present embodiment, the condition changing circuit (gate resistance changing circuit 60) switches the driving condition of the switching element Q1 based on the driving signal (gate pulse) in accordance with the on/off of the step-down circuit 30.
With this configuration, the driving condition of the switching element Q1 can be switched to an appropriate condition in accordance with the switching of the output voltage Vo.
Further, according to the present embodiment, the step-down detection circuit (step-down operation condition detection circuit 70) detects the operation condition of the step-down circuit 30, and the condition change circuit (overcurrent detection condition correction circuit 50a, gate resistance change circuit 60a) changes the operation condition in accordance with the operation condition of the step-down circuit 30.
With this configuration, the change in the output voltage Vo can be detected on the primary side in accordance with the operating state of the step-down circuit 30.
Further, according to the present embodiment, the step-down circuit 30 includes the transistor Q2, and adjusts the voltage between the main terminals (collector-emitter voltage Vce) of the transistor Q2, which is a step-down amount, in accordance with the voltage of the auxiliary winding P2Q2) The voltage between collector and emitter Vce is detected by a step-down detection circuit (step-down operation condition detection circuit 70)Q2As the operating condition of the step-down circuit 30.
With this configuration, the change in the output voltage Vo can be detected on the primary side in accordance with the step-down amount of the step-down circuit 30.
Further, according to the present embodiment, the primary side control circuit (the primary side control IC 10) has an overcurrent detection function of detecting an overcurrent based on a current value (drain current Id) flowing through the switching element Q1 inputted from the Cs terminal, and the condition change circuit (the overcurrent detection condition correction circuit 50a) changes an input condition of inputting the current value (drain current Id) to the Cs input terminal in accordance with an operation state of the step-down circuit 30.
With this configuration, even if the output voltage Vo is changed, the overcurrent protection operation can be stably performed.
Further, according to the present embodiment, the condition changing circuit (gate resistance changing circuit 60a) changes the driving condition of the switching element Q1 based on the driving signal (gate pulse) in accordance with the operating state of the step-down circuit 30.
With this configuration, the driving condition of the switching element Q1 can be changed to an appropriate condition in accordance with the change in the output voltage Vo.
Although the present invention has been described above with reference to specific embodiments, the above embodiments are merely examples, and it is needless to say that modifications and implementations can be made without departing from the scope of the present invention.
Description of the reference symbols
1. 1 a: a switching power supply device; and Vi: inputting a voltage; c1, C21: a smoothing capacitor; CC1, CC 2: a current source; t: a transformer T; 10: a primary-side control IC; 20. 20 a: a secondary side circuit; q1: a switching element; q2: a transistor; q3, Q4, Q5: a switching element; d1, D2, D3, D21: a diode; ZD 1: a Zener diode; R1-R10: a resistance; c2: a capacitor; 30: a voltage reduction circuit; 40: a step-down operation detection circuit; 50. 50 a: an overcurrent detection condition correction circuit; 60. 60 a: a gate resistance changing circuit; 70: a step-down operation status detection circuit.
Claims (8)
1. A switching power supply device that transmits input power applied to a primary coil of a transformer to a secondary coil of the transformer by on/off controlling a switching element connected to the primary coil, and transmits power from the secondary coil to an auxiliary coil of the transformer, thereby generating a drive power supply of a primary-side control circuit that on/off controls the switching element from the auxiliary coil, the switching power supply device comprising:
a voltage reduction circuit that is turned on/off in accordance with the voltage of the auxiliary coil, and supplies a constant voltage obtained by reducing the voltage of the auxiliary coil to the primary control circuit as the drive power supply when the voltage reduction circuit is turned on;
a step-down detection circuit that detects an operation of the step-down circuit; and
a condition changing circuit for changing an operation condition of a primary side by using a drive signal for driving the switching element in accordance with an operation of the voltage-reducing circuit,
the step-down detection circuit detects on/off of the step-down circuit,
the condition changing circuit switches the operating condition in response to ON/OFF of the step-down circuit,
the primary side control circuit has an overcurrent detection function of detecting an overcurrent based on a value of a current flowing through the switching element input from an overcurrent detection input terminal,
the condition changing circuit switches an input condition for inputting the current value to the overcurrent detection input terminal in accordance with on/off of the voltage reducing circuit.
2. Switching power supply unit according to claim 1,
the constant voltage supplied from the voltage reduction circuit to the primary side control circuit is higher than a start voltage of the primary side control circuit.
3. Switching power supply unit according to claim 1,
the voltage reduction circuit includes a Zener diode which is turned on/off in accordance with a voltage of the auxiliary winding,
the step-down detection circuit detects on/off of the step-down circuit according to on/off of the zener diode.
4. Switching power supply unit according to claim 1,
the condition changing circuit switches a driving condition of the switching element based on the driving signal in accordance with on/off of the voltage lowering circuit.
5. Switching power supply unit according to claim 1,
the step-down detection circuit detects an operation condition of the step-down circuit,
the condition changing circuit changes the operating condition in accordance with an operating condition of the voltage step-down circuit.
6. Switching power supply unit according to claim 5,
the step-down circuit includes a transistor, a voltage between main terminals of the transistor is adjusted in accordance with a voltage of the auxiliary winding,
the step-down detection circuit detects a voltage between the main terminals of the transistors as an operation state of the step-down circuit.
7. Switching power supply unit according to claim 5,
the condition changing circuit changes an input condition for inputting the current value to the overcurrent detection input terminal in accordance with an operating condition of the voltage reducing circuit.
8. Switching power supply unit according to claim 5,
the condition changing circuit changes a driving condition of the switching element based on the driving signal according to an operating condition of the voltage reducing circuit.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/JP2016/068635 WO2017221366A1 (en) | 2016-06-23 | 2016-06-23 | Switching power supply device |
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| CN109314465A CN109314465A (en) | 2019-02-05 |
| CN109314465B true CN109314465B (en) | 2020-09-18 |
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|---|---|---|---|---|
| CN109039028B (en) * | 2018-07-09 | 2020-06-16 | 华为技术有限公司 | Control circuit applied to power adapter and power adapter |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000152626A (en) * | 1998-11-05 | 2000-05-30 | Omron Corp | Stabilizing power source |
| JP2003111399A (en) * | 2001-09-27 | 2003-04-11 | Sanken Electric Co Ltd | Dc-dc converter |
| JP2004166319A (en) * | 2002-11-08 | 2004-06-10 | Murata Mfg Co Ltd | Dc-dc converter |
| CN203590533U (en) * | 2013-10-12 | 2014-05-07 | 广州众恒光电科技有限公司 | LED power supply with power adjustable |
| CN103857148A (en) * | 2012-11-30 | 2014-06-11 | 硅工厂股份有限公司 | Power supply apparatus for LED lighting and LED lighting apparatus using the same |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4118101B2 (en) * | 2002-08-23 | 2008-07-16 | 新電元工業株式会社 | Power circuit |
-
2016
- 2016-06-23 WO PCT/JP2016/068635 patent/WO2017221366A1/en active Application Filing
- 2016-06-23 CN CN201680086428.XA patent/CN109314465B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000152626A (en) * | 1998-11-05 | 2000-05-30 | Omron Corp | Stabilizing power source |
| JP2003111399A (en) * | 2001-09-27 | 2003-04-11 | Sanken Electric Co Ltd | Dc-dc converter |
| JP2004166319A (en) * | 2002-11-08 | 2004-06-10 | Murata Mfg Co Ltd | Dc-dc converter |
| CN103857148A (en) * | 2012-11-30 | 2014-06-11 | 硅工厂股份有限公司 | Power supply apparatus for LED lighting and LED lighting apparatus using the same |
| CN203590533U (en) * | 2013-10-12 | 2014-05-07 | 广州众恒光电科技有限公司 | LED power supply with power adjustable |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109314465A (en) | 2019-02-05 |
| WO2017221366A1 (en) | 2017-12-28 |
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