TW201840115A - Frequency control circuit - Google Patents

Abstract

A frequency control circuit comprises a current detection unit and a frequency control unit. The current detection unit is used to sense a output current of a switching power supply device and decide whether or not to generate a frequency up control signal according to the output current. The frequency control unit is connected to a pulse width modulation control circuit of the switching power supply device, the frequency control unit is used to receive a frequency up control signal and a voltage of the switching power supply device on the primary side, the frequency control unit determines whether the pulse width modulation control circuit increases its operating frequency according to the frequency up control signal and the voltage.

Description

Up-conversion control circuit

The present invention relates to an up-conversion control circuit, and more particularly to an up-conversion control circuit suitable for a switched-mode power supply device.

At present, the switching power supply device often uses a pulse width modulation control circuit (PWM) to detect the feedback voltage to control the operating frequency adjustment mechanism of the pulse width modulation control circuit. In order to meet the design requirements of the switching power supply device for miniaturization and the demand of high-energy schools in the future, the switching power supply device further reduces the size of the transformer, and still uses the same maximum magnetic flux in the design theory, and avoids the magnetic saturation phenomenon, but for the high Energy efficiency requirements and optimized transformer utilization, miniaturized design requirements provide an overall increase in operating frequency, which in turn leads to additional problems. For example, because the operating frequency is increased, when the output current of the switching power supply device is low, the operating frequency is also increased, and the switching loss is accordingly increased, resulting in lower average efficiency.

In order to solve the above drawbacks, the present invention provides an embodiment of an up-conversion control circuit, the up-conversion control circuit includes a current detecting unit and an up-conversion control unit, and the current detecting unit is configured to sense an output current of the switching power supply device. And determining whether to generate an up-conversion control signal according to the output current, the up-conversion control unit is coupled to the pulse width modulation control circuit of the switching power supply device, and the up-conversion control unit receives the up-conversion control signal and the switched-mode power supply device once The side output voltage, the up-conversion control unit determines whether to enable the pulse width modulation control circuit to increase its operating frequency according to the up-conversion control signal and the primary-side output voltage.

In order to solve the above drawbacks, the present invention provides another embodiment of an up-conversion control circuit, the up-conversion control circuit includes a current detection unit and an up-conversion control unit, and the current detection unit is configured to sense an output of the switched-mode power supply device. Current, and determining whether to generate an up-conversion control signal according to the output current, the up-conversion control circuit is coupled with the pulse width modulation control circuit of the switching power supply device, and the up-conversion control unit receives the up-conversion control signal and the first voltage, and up-converts The control unit determines whether to enable the pulse width modulation control circuit to increase its operating frequency according to the up-conversion control signal and the first voltage.

In other embodiments, the switched power supply device includes a rectifier circuit for outputting a rectified output voltage, and the rectified output voltage is the first voltage.

In summary, the up-conversion control circuit of the present invention can detect the output current of the switching power supply device by the current detecting unit, and determine whether to make the output current according to the up-conversion control unit and the selected voltage. The pulse width modulation control circuit increases its operating frequency, thereby adjusting the operating frequency of the pulse width modulation control circuit to effectively solve the limitation of switching loss and low average efficiency.

The above and other objects, features, and advantages of the present invention will become more apparent from the description of the appended claims.

Please refer to FIG. 1. FIG. 1 is a schematic diagram of a first embodiment of a switching power supply device PSU. The switching power supply device PSU includes an input end 11 and an output end 12. The switching power supply device PSU has a first end 111 of the input end 11 And the second terminal 112 receives the input voltage VIN and converts the input voltage VIN into an output voltage VOUT, and the switching power supply device PSU transmits the output voltage VOUT to the first terminal 121 and the second terminal 122 of the output terminal 12 The required load, wherein the input voltage VIN can be an alternating voltage, and the output voltage VOUT can be a direct current voltage. The switching power supply device PSU further includes a first rectifier circuit 13, a transformer circuit 14, a switch circuit 15, a pulse width modulation control circuit 16, a second rectifier circuit 18, an energy storage unit 19, an up-conversion control circuit, and a feedback unit 21. The up-conversion control circuit further includes an up-conversion control unit 17 and a current detecting unit 20.

The first rectifying circuit 13 can be a bridge rectifier that rectifies the input voltage VIN and outputs a rectified output voltage. The voltage converter circuit 14 is coupled to the first rectifier circuit 13, and the voltage transformer circuit 14 is configured to transform the rectified output voltage into a desired voltage value. The second rectifier circuit 18 is coupled to the secondary side of the transformer circuit 14. The energy storage unit 19 is coupled to the second rectifier circuit 18 and the secondary side of the transformer circuit 14. The second rectifier circuit 18 and the energy storage unit 19 are used. The received voltage is rectified and filtered, and the above-mentioned output voltage VOUT is output. The current detecting unit 20 is coupled to the output end 12 of the switching power supply device PSU. The current detecting unit 20 is configured to sense the output current I _{O of the} switching power supply device PSU and determine whether to generate according to the output current I _{O .} The up-conversion control signal S2, wherein the up-conversion control signal S2 can be an optical signal. The feedback unit 21 is coupled to the output terminal 12 of the switching power supply device PSU and the pulse width modulation control circuit 16. The feedback unit 21 is configured to determine whether to generate the feedback signal S1 according to the output voltage VOUT, and the feedback signal is generated. S1 is transmitted to the pulse width modulation control circuit 16, wherein the feedback signal S1 can be an optical signal. The switch circuit 15 is connected in series with the primary side coil of the transformer circuit 14. The switch circuit 15 is configured to determine whether to allow current to pass through the primary side coil of the transformer circuit 14 according to the pulse width modulation signal PWM outputted by the pulse width modulation control circuit 16. The up-conversion control unit 17 is coupled to the pulse width modulation control circuit 16 of the switching power supply device PSU and the other primary side coil. The primary side coil is, for example, an auxiliary coil, and is configured to output a primary side output voltage V _O1 . The primary side output voltage V _O1 is a negative voltage. The up-conversion control unit 17 receives the up-conversion control signal S2 and the primary-side output voltage V _O1 , and the up-conversion control unit 17 is configured to determine whether to make the pulse width modulation control according to the up-conversion control signal S2 and the primary-side output voltage V _{O1 .} Circuit 16 increases its operating frequency.

The up-conversion control unit 17 further includes a diode D1, a resistor R1, a resistor R2, a signal receiving unit 171, a transistor OP1, and a diode DZ1. One end of the diode D1 is configured to receive the primary side output voltage V _O1 , and the other end of the diode D1 is coupled to the first high voltage level VCC . One end of the resistor R1 is coupled to the other end of the diode D1, one end of the resistor R2 is coupled to the other end of the resistor R1, and the other end of the resistor R2 receives the primary side output voltage V _O1 . One end of the signal receiving unit 171 is coupled to the other end of the resistor R1, and the signal receiving unit 171 is configured to receive the up-converting control signal S2. The first end of the transistor OP1 is coupled to the pulse width modulation control circuit 16, and the second end of the transistor OP1 is coupled to the other end of the signal receiving unit 171. One end of the diode DZ1 is coupled to the third end of the transistor OP1, and the other end of the diode DZ1 is coupled to the first low voltage level VSS, wherein the diode DZ1 can be a Zener diode.

The current detecting unit 20 includes a resistor RO, a voltage dividing unit 201, a comparing unit 202, a voltage stabilizing diode Q1, and a signal transmitting unit 203. One end of the resistor RO is coupled to the energy storage unit 19, and the other end is coupled to the second end 122 of the output terminal 12, and the resistor RO is used to generate an output current I _O . One end of the voltage dividing unit 201 is coupled to the other end of the resistor RO for generating an induced voltage corresponding to the output current I _O . In this embodiment, the voltage dividing unit 201 includes a resistor R3 and a resistor R4. One end of the resistor R3 is coupled to the other end of the resistor RO, and the other end of the resistor R3 generates an induced voltage. One end of the resistor R4 is coupled to the other end of the resistor R3. The other end of the resistor R4 is coupled to the second low voltage level GND, wherein the second low voltage level GND can be a ground level. The first input of the comparison unit 202 is coupled to the other end of the resistor R3 and receives the induced voltage, and the second input of the comparison unit 202 receives the reference voltage VF1. The first end of the voltage stabilizing diode Q1 is coupled to the output end of the comparing unit 202, and the second end of the voltage stabilizing diode Q1 is coupled to the second low voltage level GND, wherein the comparing unit is in this embodiment. The first input of 202 may be a negative input (-) and the second input of comparison unit 202 may be a positive input (+). One end of the signal transmitting unit 203 is coupled to the third end of the voltage stabilizing diode Q1, and the other end of the signal transmitting unit 203 receives the second high voltage level VH, wherein the second high voltage level VH can be the output voltage VOUT. The signal transmission unit 203 is configured to generate the above-mentioned up-conversion control signal S2.

The feedback unit 21 includes a resistor R5, a resistor R6, a voltage regulator diode Q2, a signal transmission unit 211, and a signal receiving unit 212. One end of the resistor R5 is coupled to the first end 121 of the output terminal 12, one end of the resistor R6 is coupled to the other end of the resistor R5, and the other end of the resistor R6 is coupled to the second low voltage level GND. The first end of the voltage stabilizing diode Q2 is coupled to the other end of the resistor R5, and the second end of the voltage stabilizing diode Q2 is coupled to the other end of the resistor R6, and the third end of the voltage stabilizing diode Q2 is connected with the signal One end of the transfer unit 211 is coupled. The other end of the signal transmission unit 211 is coupled to the end of the resistor R5. The signal transmission unit 211 is configured to generate the feedback signal S1. One end of the signal receiving unit 212 is coupled to the pulse width modulation control circuit 16 and the up-conversion control unit 17. One end of the signal receiving unit 212 is coupled to the first end of the transistor OP1, and the other end of the signal receiving unit 212 is coupled to the first end of the signal receiving unit 212. A low voltage level VSS is coupled, wherein the signal receiving unit 212 is configured to receive the feedback signal S1.

Next, the operation mode of the up-conversion control circuit will be described below with reference to FIG. First, the feedback unit 21 drives the voltage stabilizing diode Q2 according to the voltage division of the output voltage VOUT on the resistor R5 and the resistor R6, so that a current flows through the signal transmitting unit 211, and the signal transmitting unit 211 thus generates the feedback signal S1. . The signal receiving unit 212 of the corresponding signal transmitting unit 211 is turned on after receiving the feedback signal S1 and generates a feedback voltage at one end of the signal receiving unit 212. At the same time, the current detecting unit 20 generates an output current I _O by the resistor RO, and generates an induced voltage by the voltage dividing unit 201. When the induced voltage is less than the reference voltage VF1, the voltage stabilizing diode Q1 is driven, and the signal transmitting unit 203 Therefore, the up-conversion control signal S2 is generated. When the signal receiving unit 171 of the corresponding signal transmitting unit 203 receives the up-converting control signal S2, the signal receiving unit 171 is turned on at one end and the other end thereof, and the primary side output voltage V _{O1 is} made on the resistor R1 and the resistor R2. The divided voltage is a positive voltage, the second end of the transistor OP1 receives a positive voltage due to the conduction of the signal receiving unit 171, the transistor OP1 is thus enabled, and the first end and the third end of the transistor OP1 are electrically connected to each other, The voltage at the first end of the transistor OP1 is stabilized across the voltage across the diode DZ1, and the pulse width modulation control circuit 16 therefore determines that the operating frequency is not increased according to the voltage at the first end of the transistor OP1.

On the other hand, when the induced voltage is greater than the reference voltage VF1, that is, the output current I _{O is} large, the voltage stabilizing diode Q1 is disabled, and the signal transmitting unit 203 will not generate the up-converting control signal S2, so the corresponding signal receiving Unit 171 cannot be turned on by up-conversion control signal S2, and transistor OP1 remains off. In addition, the primary side output voltage V _O1 generates a lower negative voltage value relative to the output voltage VOUT, and maintains the divided voltage on the resistor R1 and the resistor R2 at a lower voltage value or a negative voltage value, if the signal receiving unit 171 interferes with the signal. Or other factors, the transistor OP1 will still be turned off due to the negative voltage value, and the up-conversion control unit 17 is disabled. Therefore, in this example, since the feedback voltage is not stabilized by the up-conversion control unit 17 at a relatively low voltage, the pulse width modulation control circuit 16 will directly adjust the operating frequency according to the feedback voltage, that is, at this time. The output voltage VOUT is relatively large, so the pulse width modulation control circuit 16 is required to adjust the operating frequency to adjust the output voltage VOUT, that is, when the load required voltage is greater than the set voltage value, the up-conversion control unit 17 and the current detecting unit 20 The pulse width modulation control circuit 16 is then adjusted to operate its frequency based on the feedback voltage.

2A, FIG. 2A is a schematic diagram of the second embodiment of the switching power supply device PSU, and FIG. 2A has the same components as those of FIG. 1 , and FIG. 2A differs from FIG. 1 in the up-conversion control of FIG. 2A . The unit 17 includes a diode D2, a diode D3, a resistor R7, a resistor R8, a signal receiving unit 171, a transistor OP1, a transistor OP2, and a diode DZ1. One end of the diode D2 is coupled to the first end 111 of the input end 11, one end of the diode D3 is coupled to the second end 112 of the input end 11, and the other ends of the diode D2 and the diode D3 are connected to each other. Coupling. One end of the resistor R7 is coupled to the other end of the diode D2 and the diode D3. One end of the resistor R8 is coupled to the other end of the resistor R7, and the other end of the resistor R8 is coupled to the first low voltage level VSS. The first end of the transistor OP2 is coupled to the other end of the resistor R7, and the second end of the transistor OP2 is coupled to the first low voltage level VSS. One end of the signal receiving unit 171 receives the reference voltage VF2, and the other end of the signal receiving unit 171 is coupled to the third end of the transistor OP2. The first end of the transistor OP1 is coupled to the pulse width modulation control circuit 16, and the second end of the transistor OP1 is coupled to the third end of the transistor OP2. One end of the diode DZ1 is coupled to the third end of the transistor OP1, and the other end of the diode DZ1 is coupled to the first low voltage level VSS.

Next, the operation mode of the up-conversion control circuit will be described below with reference to FIG. 2A, and the same portions as those of FIG. 1 will not be described again. When the signal receiving unit 171 turns on one end and the other end thereof according to the above-mentioned up-conversion control signal S2, the voltage division of the input voltage VIN on the resistor R7 and the resistor R8 turns off the transistor OP2, and the second end of the transistor OP1 is closed. The signal receiving unit 171 is turned on to receive the reference voltage VF2, and the voltage at the first end of the transistor OP1 is turned on and stabilized in the voltage across the diode DZ1. Therefore, the pulse width modulation control circuit 16 It is judged that the operating frequency is not increased according to the current voltage of the first end of the transistor OP1. On the contrary, when the output current I _{O is} large, the voltage stabilizing diode Q1 is disabled, the signal transmitting unit 203 does not generate the up-converting control signal S2, the signal receiving unit 171 is not turned on, and the input voltage is maintained when the transistor OP1 is kept off. The voltage division of VIN on the resistor R7 and the resistor R8 is increased to turn on the transistor OP2, and the transistor OP2 maintains the voltage of the second terminal of the transistor OP1 at the first low voltage level VSS, and the transistor OP1 is turned off, and the up-conversion control unit 17 is turned off, so the pulse width modulation control circuit 16 will directly adjust the operating frequency according to the feedback voltage, that is, when the voltage required by the load is greater than the set voltage value, the up-conversion control unit 17 and the current detecting unit 20 make the pulse The wide modulation control circuit 16 adjusts its operating frequency based on the feedback voltage.

2B, FIG. 2B is a schematic diagram of a third embodiment of the switching power supply device PSU, and FIG. 2B has the same components as those of FIG. 2A. The difference between FIG. 2B and FIG. 2A is that one end of the resistor R7 is A rectifying circuit 13 is coupled to and receives the rectified output voltage, and determines whether to enable the transistor OP2 according to the rectified output voltage. The operation method of FIG. 2B is the same as that of FIG. 2A, and therefore will not be described below.

Referring to FIG. 3, FIG. 3 is a schematic diagram of Embodiment 4 of the switching power supply device PSU, and FIG. 3 has the same components as those of FIG. The difference between FIG. 3 and FIG. 1 is that the up-conversion control unit 17 further includes a voltage detection circuit 172. The voltage detection circuit 172 includes a resistor R9, a resistor R10, a comparison unit 1721, a comparison unit 1722, and a transistor OP3. One end of the resistor R9 receives the reference voltage VF3, one end of the resistor R10 is coupled to the other end of the resistor R9, and the other end of the resistor R10 is coupled to the first low voltage level VSS. The first input end of the comparison unit 1721 receives the reference voltage VF3, the second input end of the comparison unit 1721 is coupled to the other end of the resistor R1, and the output end of the comparison unit 1721 is coupled to one end of the signal receiving unit 171, wherein In an embodiment, the first input of the comparison unit 1721 may be a positive input (+), and the second input of the comparison unit 1721 may be a negative input (-). The first input end of the comparison unit 1722 is coupled to one end of the resistor R10, the second input end of the comparison unit 1722 is coupled to the other end of the resistor R1, and the output end of the comparison unit 1722 is coupled to the transistor OP3. In an embodiment, the first input of the comparison unit 1722 may be a positive input (+), and the second input of the comparison unit 1722 may be a negative input (-). The first end of the transistor OP3 is coupled to the other end of the signal receiving unit 171, the second end of the transistor OP3 is coupled to the output end of the comparing unit 1722, and the third end of the transistor OP3 is connected to the first low voltage level VSS. Coupling.

In this embodiment, when the signal receiving unit 171 turns on one end and the other end thereof according to the above-mentioned up-conversion control signal S2, the voltage of the first input end of the comparing unit 1721 is greater than the voltage of the second input end, and the comparing unit 1722 The voltage of the first input terminal is lower than the voltage of the second input terminal, and the transistor OP3 is disabled due to the voltage of the output terminal of the comparison unit 1722. The transistor OP1 can receive the voltage of the output terminal of the comparison unit 1721 by the turned-on signal receiving unit 171. It is enabled to stabilize the voltage at the first end of the transistor OP1 across the voltage across the diode DZ1. Therefore, the pulse width modulation control circuit 16 determines that the operating frequency is not increased according to the current voltage. When the voltage of the first input terminal of the comparison unit 1722 is greater than the voltage of the second input terminal, the transistor OP3 is enabled by the voltage of the output terminal of the comparison unit 1722, so the voltage of the second terminal of the transistor OP1 is thus stabilized at the first low voltage level. VSS, the transistor OP1 is off, the up-conversion control unit 17 is off, and the pulse width modulation control circuit 16 will directly adjust the operating frequency according to the feedback voltage. By this mechanism, the voltage range enabled by the up-conversion control unit 17 can be further limited, that is, the voltage range is limited to the voltage of the first input terminal of the comparison unit 1721 to the voltage of the first input terminal of the comparison unit 1722, and in this embodiment. The voltage of the first input terminal of the comparison unit 1721 is greater than the voltage of the first input terminal of the comparison unit 1722.

Referring to FIG. 4A, FIG. 4A is a schematic diagram of Embodiment 5 of the switching power supply device PSU. The difference between FIG. 4A and FIG. 2A is that the up-conversion control unit 17 further includes a voltage detection circuit 172, and the voltage detection circuit 172 includes Resistor R11, resistor R12, comparison unit 1723, and comparison unit 1724. One end of the resistor R11 receives the reference voltage VF4, and the other end of the resistor R11 is coupled to the comparison unit 1724. One end of the resistor R12 receives the reference voltage VF4, and the other end of the resistor R12 is coupled to the first low voltage level VSS. The first input end of the comparison unit 1723 is coupled to one end of the resistor R8, the second input end of the comparison unit 1723 receives the reference voltage VF4, and the output end of the comparison unit 1723 is coupled to one end of the signal receiving unit 171, in this embodiment. The first input terminal of the comparison unit 1723 is a positive input terminal (+), and the second input terminal of the comparison unit 1723 is a negative input terminal (-). The first input end of the comparison unit 1724 is coupled to one end of the resistor R8, the second input end of the comparison unit 1724 is coupled to the other end of the resistor R11, and the output end of the comparison unit 1724 is coupled to the first end of the transistor OP2. In this embodiment, the first input of the comparison unit 1724 is a positive input (+), and the second input of the comparison unit 1724 is a negative input (-).

In this embodiment, when the signal receiving unit 171 turns on one end and the other end thereof according to the above-mentioned up-conversion control signal S2, the voltage of the first input end of the comparing unit 1723 is greater than the voltage of the second input end and the comparing unit 1724 The voltage of the first input terminal is lower than the voltage of the second input terminal. Therefore, the transistor OP1 can be enabled by receiving the voltage of the output terminal of the comparison unit 1723 by the turned-on signal receiving unit 171, and the voltage of the first end of the transistor OP1 is stabilized. The voltage across the diode DZ1 is such that the pulse width modulation control circuit 16 determines that the operating frequency is not increased based on the current voltage. When the voltage of the first input terminal of the comparison unit 1724 is greater than the voltage of the second input terminal, the transistor OP3 is enabled by the voltage of the output terminal of the comparison unit 1723, so the voltage of the second terminal of the transistor OP1 is thus stabilized at the first low voltage level. VSS, the transistor OP1 is off, the up-conversion control unit 17 is off, and the pulse width modulation control circuit 16 will directly adjust the operating frequency according to the feedback voltage. By this mechanism, the voltage range enabled by the up-conversion control unit 17 can be further limited, that is, the voltage range is limited to the voltage of the second input terminal of the comparison unit 1723 to the second input terminal of the comparison unit 1724, and the comparison unit 1723 The voltage at the two inputs is less than the voltage at the second input of the comparison unit 1724.

4B, FIG. 4B is a schematic diagram of Embodiment 6 of the switching power supply device PSU, and FIG. 4B is the same component as FIG. 4A with the same component symbol, and FIG. 4B differs from FIG. 4A in that one end of the resistor R7 is A rectifying circuit 13 is coupled to and receives the rectified output voltage, and determines whether to enable the transistor OP2 according to the rectified output voltage. The operation method of FIG. 4B is the same as that of FIG. 4A, and therefore will not be described below.

In summary, the up-conversion control circuit of the present invention can detect the output current I _{O of the} switching power supply device PSU and the selected voltage by the current detecting unit 20 to determine the voltage at the first end of the transistor OP1. The pulse width modulation control circuit 16 determines whether to increase the operating frequency according to the voltage of the first end of the transistor OP1, thereby effectively preventing the pulse width modulation control circuit 16 from operating at a higher operating frequency under light load conditions. , effectively solve the shortcomings of switching loss and low average efficiency.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and those skilled in the art can make some modifications and retouchings without departing from the spirit and scope of the present invention. The time defined in the scope of the patent application is subject to change.

PSU‧‧‧Switching power supply unit

11‧‧‧ input

12‧‧‧ Output

111, 121‧‧‧ first end

112, 122‧‧‧ second end

VIN‧‧‧ input voltage

VOUT‧‧‧ output voltage

13‧‧‧First rectifier circuit

14‧‧‧Transformer circuit

15‧‧‧Switch circuit

16‧‧‧ Pulse width modulation control circuit

17‧‧‧Upconversion Control Unit

171‧‧‧Signal receiving unit

172‧‧‧Voltage detection circuit

202, 1721, 1722, 1723, 1724‧‧‧ comparison unit

18‧‧‧Second rectifier circuit

19‧‧‧ Energy storage unit

20‧‧‧current detection unit

201‧‧‧Dividing unit

203‧‧‧Signal transmission unit

21‧‧‧Responsible unit

211‧‧‧Signal transmission unit

212‧‧‧Signal receiving unit

S1‧‧‧Reward signal

S2‧‧‧ Upconversion Control Signal

D1, D2, D3, DZ1‧‧‧ diodes

Q1, Q2‧‧‧ Regulators

RO, R1, R2, R3, R4, R5, R6, R7, R8, R9, R11, R12‧‧‧ resistance

OP1, OP2, OP3‧‧‧O crystal

VCC‧‧‧ first high voltage level

VSS‧‧‧First low voltage level

V _O1 ‧‧‧primary output voltage

VF1, VF2, VF3, VF4‧‧‧ reference voltage

VH‧‧‧ second high voltage level

GND‧‧‧second low voltage level

FIG. 1 is a schematic diagram of Embodiment 1 of a switching power supply device according to the present invention. 2A is a schematic view showing a second embodiment of a switching power supply device according to the present invention. 2B is a schematic diagram of Embodiment 3 of the switching power supply device of the present invention. FIG. 3 is a schematic diagram of Embodiment 4 of the switching power supply device of the present invention. 4A is a schematic diagram of Embodiment 5 of the switching power supply device of the present invention. 4B is a schematic diagram of Embodiment 6 of the switching power supply device of the present invention.

Claims (10)

An up-conversion control circuit is applicable to a switching power supply device, the up-conversion control circuit includes: a current detecting unit for sensing an output current of the switching power supply device, and determining whether the output current is based on the output current Generating an up-conversion control signal; and an up-conversion control unit coupled to a pulse width modulation control circuit of the switching power supply device, the up-conversion control unit receiving the up-conversion control signal and the switching power supply device The primary side output voltage, the up-conversion control unit determines whether to increase the operating frequency of the pulse width modulation control circuit according to the up-conversion control signal and the primary-side output voltage. The up-conversion control circuit of claim 1, wherein the up-conversion control unit comprises: a first diode, one end of which receives the primary-side output voltage; and a first resistor, one end of the first resistor The other end of the diode is coupled to the second resistor, one end of the second resistor is coupled to the other end of the first resistor, and the other end of the second resistor is coupled to the one end of the first diode; The unit is coupled to the other end of the first resistor for receiving the up-conversion control signal; a first transistor having a first end coupled to the pulse width modulation control circuit, and a first transistor The second end is coupled to the other end of the signal receiving unit; and a second diode is coupled to a third end (S) of the first transistor and has a low voltage level Coupling. The up-conversion control circuit of claim 2, wherein the current detecting unit comprises: a third resistor, one end of which is coupled to an output end of the switching power supply device for generating the output current a voltage dividing unit coupled to the other end of the third resistor for generating an induced voltage corresponding to the output current; a comparing unit, the first input receiving the induced voltage and the second input receiving the second input a first voltage stabilizing diode, the first end of which is coupled to the output end of the comparing unit, the second end of which is coupled to a first low voltage; and a signal transmitting unit having one end and the first The third end of the diode is coupled to the other end, and the other end receives a high voltage level, and the signal transmitting unit is configured to generate the up-conversion control signal. The up-conversion control circuit of claim 3, wherein the up-conversion control unit further comprises a voltage detection circuit, the voltage detection circuit comprising: a first comparison unit, the first input receiving a reference a second input end coupled to the other end of the first resistor, the output end of which is coupled to the one end of the signal receiving unit; a fourth resistor having one end and the first end of the first comparing unit The second input unit has a first input end coupled to the other end of the fourth resistor, and a second input end coupled to the other end of the first resistor; a fifth resistor, One end is coupled to the first input end of the second comparison unit, and the other end is coupled to the low voltage level; and a second transistor is coupled to the other end of the signal receiving unit The second end is coupled to the output end of the second comparator, and the third end is coupled to the low voltage level. An up-conversion control circuit is applicable to a switching power supply device, the up-conversion control circuit includes: a current detecting unit for sensing an output current of the switching power supply device, and determining whether the output current is based on the output current Generating an up-conversion control signal; and an up-conversion control unit coupled to a pulse width modulation control circuit of the switching power supply device, the up-conversion control unit receiving the up-conversion control signal and a first voltage, The up-conversion control unit determines whether to increase the operating frequency of the pulse width modulation control circuit according to the up-conversion control signal and the first voltage. The up-conversion control circuit of claim 5, wherein the up-conversion control unit comprises: a first resistor having one end receiving the first voltage; and a second resistor having one end and the first resistor One end is coupled to the other end and coupled to a low voltage level; a first transistor having a first end (B) coupled to the other end of the first resistor, and a second end coupled to the low voltage a signal receiving unit, one end of which receives a reference voltage, and the other end of which is coupled to the third end of the first transistor, the signal receiving unit is configured to receive the up-converting control signal; a first end of the crystal coupled to the pulse width modulation control circuit, a second end coupled to the third end of the first transistor, and a first diode having one end and the second The third end (S) of the crystal is coupled, and the other end of the crystal is coupled to the low voltage level. The up-conversion control circuit of claim 6, wherein the switching power supply device comprises a rectifier circuit for outputting a rectified output voltage, the rectified output voltage being the first voltage. The up-conversion control circuit of claim 6, wherein the switching power supply device comprises an input terminal for receiving an input voltage, the up-conversion control unit further comprising: a first diode, One end is coupled to the input voltage, and the other end is configured to output the first voltage; and a second diode is coupled to the input voltage at one end and outputting the first voltage at the other end. The up-conversion control circuit of claim 6, wherein the up-conversion control unit further comprises a voltage detection circuit, the voltage detection circuit comprising: a first comparison unit, the first input end and the first The other end of the resistor is coupled to the second input terminal for receiving the reference voltage, and the output end is coupled to the one end of the signal receiving unit; a third resistor is coupled to the reference voltage at one end thereof; a second comparison unit having a first input end coupled to the other end of the first resistor, a second input end coupled to the other end of the third resistor, and an output end and the first end of the first transistor One end is coupled to the first resistor, one end of which is coupled to the reference voltage, and the other end of which is coupled to the low voltage level. The up-conversion control circuit of claim 9, wherein the current detecting unit comprises: a fifth resistor, one end of which is coupled to an output end of the switching power supply device for generating the output current a voltage dividing unit coupled to the other end of the fifth resistor for generating an induced voltage corresponding to the output current; a comparing unit, the first input receiving the induced voltage and the second input receiving the second input a first voltage stabilizing diode, the first end of which is coupled to the output end of the comparing unit, the second end of which is coupled to a first low voltage; and a signal transmitting unit having one end and the first A third end of the voltage stabilizing diode is coupled, and the other end receives a high voltage level, and the signal transmitting unit is configured to generate the up-converting control signal.