CN101753013A - switching power supply - Google Patents

Abstract

Disclosed is a switching power supply with a power factor correction controller, which includes a boost converter, a current detection unit, an arithmetic unit, and a switching control unit. The current detection unit may be used to detect or drive a current through the energy transmission means, which is usually constituted and implemented by a diode or a switch. The current detection unit may also be used to detect an inductor current or a switch current. In the case of direct detection of no load, the arithmetic unit can calculate the optimum switch on-time or when to turn off the switch by the current detection unit. The disclosed invention removes the circuitry required to sense the voltage across the load terminal as in the prior art, reducing overall weight and system cost. The disclosed invention also improves the power factor of the system by detecting the transmission current pattern of the energy transfer, in contrast to the prior art.

Description

switching power supply

technical field

The present invention relates to switched mode power supplies (SMPS), and more particularly to power factor corrected (PFC) switched mode power supplies.

Background technique

Although there are many types of switch-mode power supplies and there are too many to enumerate, but looking at the previous related known technologies, the stable method of controlling the output voltage of the power supply is nothing more than intercepting a signal from the output load terminal to communicate with the internal The signal comparison is moderately adjusted by controlling the internal circuit to maintain the stability of the voltage output and provide low-power electronic consumer devices with stable power requirements.

However, although these technologies can provide a stable output voltage source, they must pass through the detection circuit at the load end, which not only increases the production cost of this type of power supply, but also occupies a certain amount of space inside it, resulting in a larger and heavier device. Larger, so the power supply that achieves the purpose of voltage regulation by comparing the load sensing voltage has inevitable disadvantages.

When the general mains supply power, its power factor (PF) should be 1 (that is, 100%). When the electricity is transmitted to the client, it may cause some power consumption due to factors such as long line distance or current phase deviation, resulting in Most of its power factors may be attenuated to 60-70%. Generally, the traditional active switching power supply has a power factor correction (hereinafter referred to as PFC) function, that is, it has a power factor close to 1 that can be improved. Therefore, the switching power supply uses the PFC controller to reduce the loss of the power supply under the condition of resonance and bias current.

Please refer to FIG. 1 , which is a circuit block diagram of a switching power supply shown in the prior art. Wherein the PFC switching power supply 1 is generally equipped with a boost converter 11 and a PFC controller 12; wherein, the boost converter 11 has an inductor 114, a resistor 117, an output stage 118 and an energy transmission device, and the energy transmission device usually uses a diode 115 or a transistor switch 116 for operation. The PFC controller 12 has an AC voltage detection unit 121, an inductor current detection unit 122, a load detection unit 123, an arithmetic unit 124, a comparator 125, and a switch control unit 126, wherein the load detection unit 123 detects the voltage value of the load output stage 118 To control the switch 116 and the diode 115 to be turned on or off, so as to achieve the effect of improving the power factor and provide a regulated DC voltage output.

Please refer to FIG. 2 , which is a circuit block diagram of another switching power supply shown in the prior art. Wherein the PFC switching power supply 2 is generally equipped with a boost converter 21 and a PFC controller 22; wherein, the boost converter 21 has an inductor 214, an output stage 217 and an energy transmission device, and the energy transmission device usually uses a diode 215 or a Transistor switch 216 operates. The PFC controller 22 has an AC voltage detection unit 221, an inductor current detection unit 222, a load detection unit 223, an operation unit 224, a switch conduction time unit 225, and a switch control unit 226, wherein the PFC controller 22 is controlled by the load detection unit 223. Detect the voltage of the load output stage 217 to control the on or off of the switch and the diode, so as to achieve the effect of improving the power factor and provide a regulated DC voltage output.

Typically a PFC controller can operate in continuous conduction mode (CCM), critical conduction mode (CRM) or discontinuous conduction mode (DCM). The choice to operate in CRM or DCM mode is based on the consideration of low power consumption applications. A common way to provide a boost converter for output load regulation is to directly sense the output voltage (eg, the operation of a load detection unit). After the load detection unit detects the output voltage, it is fed back to the PFC controller for comparison, so as to adjust the on/off time of the switch. This common approach to complex system design adds unnecessarily to board area and component space, regardless of cost.

Contents of the invention

Therefore, in view of the shortcomings of the known technology, the applicant considered a method that can eliminate the voltage detection circuit at the load end and stabilize the output voltage, and then invented the "switching power supply" of the present application to improve the shortcomings of the above-mentioned common methods.

The main purpose of the present invention is to provide a switching power supply, which can reduce the overall weight and volume by eliminating the output voltage detection circuit of the load stage, and the switching power supply also has a power factor correction function.

According to the above purpose, the present invention proposes a switching power supply on the one hand, which provides an output voltage based on the input voltage, and the switching power supply includes: a boost converter, which boosts the output voltage based on the internal inductor current, AC voltage and switching current level; and a power factor correction controller, which is coupled to the boost converter and includes: a switch current detection unit, which detects the switch current to provide a reference potential; The voltage and the switch current detected by the switch current detection unit are calculated to provide the potential to be measured; and a comparator, which uses the switch current reference potential detected by the switch current detection unit and the reference provided by the calculation unit The potentials are compared to provide a reset signal, so that the boost converter operates according to the reset signal.

According to the above idea, the input voltage of the switching power supply is commercial power.

According to the above idea, the boost converter further includes an EMI protection circuit, a rectifier, an energy storage device and an output stage.

According to the above concept, wherein the rectifier is a full-wave bridge rectifier.

According to the above idea, the energy storage device includes: an inductor, which allows the inductor current to pass through; a switch, which has an input end, a control end and an output end, the input end is coupled to the inductor, and the control end is controlled by the reset signal; a resistor coupled to the output terminal of the switch to provide the switch current; and a diode coupled to the inductor and the input terminal of the switch.

According to the above concept, wherein the switch is a transistor.

According to the above idea, the output stage includes: a filter capacitor connected in parallel with the energy storage device; and an output load connected in parallel with the filter capacitor to provide the output voltage.

According to the above idea, the power factor correction controller further includes: an inductor current detection unit, which is coupled to the boost converter, detects the inductor current and provides it to the calculation unit; an AC voltage detection unit, which is coupled to In the boost converter, detecting the AC voltage and providing it to the computing unit; and a switch control unit, coupled to the boost converter, and receiving the reset signal to control the boost converter run.

According to the above idea, the inductor current detection unit can further provide a setting signal to the switch control unit according to the inductor current, so as to further control the operation of the boost converter.

According to the above purpose, another aspect of the present invention proposes a switching power supply, which provides an output voltage based on the input voltage. The switching power supply includes: a boost converter, which boosts the output voltage based on the internal inductor current and AC voltage. level; and a power factor correction controller, which is coupled to the boost converter and includes: an operation unit, which performs operations on the inductor current and the AC voltage to provide a reset signal; and a switch conduction time unit, which The reset signal is received and transmitted so that the boost converter operates according to the reset signal.

According to the above idea, the input voltage is commercial power.

According to the above idea, the boost converter further includes an EMI protection circuit, a rectifier, an energy storage device and an output stage.

According to the above concept, wherein the rectifier is a full-wave bridge rectifier.

According to the above idea, the energy storage device includes: an inductor for the inductor current to pass through; a switch with an input end, a control end and an output end, the input end is coupled to the inductor, and the control end is controlled by the a reset signal; and a diode connected to the inductor and the input end of the switch.

According to the above concept, wherein the switch is a transistor.

According to the above idea, the output stage includes: a filter capacitor connected in parallel with the energy storage device; and an output load connected in parallel with the filter capacitor to provide the output voltage.

According to the above idea, the power factor correction controller further includes: an inductor current detection unit, which is coupled to the boost converter, detects the inductor current and provides it to the calculation unit; an AC voltage detection unit, which is coupled to In the boost converter, detecting the AC voltage and providing it to the computing unit; and a switch control unit, coupled to the boost converter, receiving the reset signal to control the operation of the boost converter .

According to the above idea, the inductor current detection unit can further provide a setting signal to the switch control unit according to the inductor current, so as to further control the operation of the boost converter.

The efficacy of the present invention is to reduce the overall weight and volume and reduce the system manufacturing cost. At the same time, when the power factor of the system is improved by detecting the current transmission mode of energy transmission, it can continuously provide stable DC voltage output to meet the requirements of the market. need.

Description of drawings

Figure 1: It shows the first known PFC switching power supply.

Figure 2: It shows the second known PFC switching power supply.

Figure 3: It shows the first PFC switching power supply of the present invention.

Figure 4: It shows the second PFC switching power supply of the present invention.

Fig. 5(a)-(c): It shows the waveforms of inductor, switch and diode current and time relationship in discontinuous current mode (DCM) of the present invention.

Detailed ways

Please refer to FIG. 3 , which shows a circuit block diagram of the first embodiment of the switching power supply proposed by the present invention. The PFC switching power supply 3 includes a boost converter 31 and a PFC controller 32 . The boost converter 31 includes a mains input stage 311 , an EMI protection circuit 312 , a rectifier 313 , an inductor 314 , a diode 315 , a switch 316 , a resistor 317 and an output stage 318 . The PFC controller 32 includes an AC voltage detection unit 321 , an inductor current detection unit 322 , a switch current detection unit 323 , a calculation unit 324 , a comparator 325 and a switch control unit 326 .

Under typical operating conditions, the mains input stage 311 receives the AC voltage VAC, which is stepped down by the EMI protection circuit 312 and rectified by the rectifier 313 to output the input voltage Vin. At this time, it is coupled to the AC voltage detection of the boost converter 31 The unit 321 detects the input voltage Vin, and another inductor current detection unit 322 coupled to the boost converter 31 also detects its inductor current IL at the same time, wherein the inductor current detection unit 322 provides a setting signal to the switch control according to the inductor current IL unit 326 to control the operation of the switch 316 in the boost converter 31 . The calculation unit 324 simultaneously receives the three signals detected by the switch current detection unit 323 , the inductor current detection unit 322 and the AC voltage detection unit 321 for calculation and processing, so as to provide the comparator 325 with a potential to be measured. The comparator 325 receives the switch current reference potential detected by the switch current detection unit 323 and compares it with the potential to be measured provided by the computing unit 324, so as to provide a reset signal to the switch control unit 326, and according to the reset signal Operation of switch 316 within boost converter 31 is controlled. When the reference potential is lower than the potential to be measured, the reset signal is responsible for closing the switch 316. At this time, more energy is allowed to be sent to the load output stage 318 to increase its output potential. When the reference potential is greater than the potential to be measured, the switch 316 is turned on. At this time, the limited energy is sent to the load output stage 318 to control its output potential not to increase.

Please refer to FIG. 4 , which shows a circuit block diagram of a second embodiment of the switching power supply 4 proposed by the present invention. The PFC switching power supply 4 includes a boost converter 41 and a PFC controller 42 . The boost converter 41 includes a mains input stage 411 , an EMI protection circuit 412 , a rectifier 413 , an inductor 414 , a diode 415 , a switch 416 and an output stage 417 . The PFC controller 42 includes an AC voltage detection unit 421 , an inductor current detection unit 422 , a calculation unit 423 , a switch conduction time unit 424 and a switch control unit 425 .

Under typical operating conditions, the mains input stage 411 receives the AC voltage VAC, which is stepped down by the EMI protection circuit 412 and rectified by the rectifier 413 to output the input voltage Vin. At this time, it is coupled to the AC voltage detection of the boost converter 41 The unit 421 detects its input voltage Vin, and another inductor current detection unit 422 coupled to the boost converter 41 also detects its inductor current IL at the same time, wherein the inductor current detection unit 422 provides a setting signal to the switch according to the inductor current IL The control unit 425 controls the operation of the switch 416 in the boost converter 41 . The operation unit 423 receives the two signals detected by the inductor current detection unit 422 and the AC voltage detection unit 421 to perform calculation processing to provide a reset signal; the switch conduction time unit 424 receives and transmits the reset signal so that the switch The control unit 425 operates the switch 416 of the boost converter 41 according to the reset signal.

Therefore, within the boost converter 41 , the switch on-time unit 424 determines whether energy is stored in the inductor 414 , and the on-time of the energy transfer diode 415 determines whether energy is transferred to the load output 417 . For the operation of the boost converter 4 in discontinuous conduction mode (DCM) or boundary conduction mode (CRM), the relationship between the conduction time of the switch 416 and the conduction time of the energy transfer diode 415 can be expressed by the following equation:

$\frac{\mathrm{<span\; class="notranslate">\; td</span>}}{\mathrm{<span\; class="notranslate">\; ton</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Vin</span>}}{\mathrm{<span\; class="notranslate">\; Vout</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Vin</span>}}$

Wherein, “td” is the turn-on time of the energy transfer diode 415 , and “ton” is the turn-on time of the switch 416 . “Vin” is the input voltage of the boost converter 41 . “Vout” is the output voltage of the boost converter 41 . As "td", "ton", and "Vin" become known, "Vout" can be derived without direct detection. In particular, as far as switching power supplies 4 are concerned, "ton" and "Vout" have a fixed relationship as follows:

$\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; ton</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; Vout</span>}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; rms</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Vout</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; Vin</span>}<span\; class="notranslate">\; )</span>$

Here "T" is the cycle time of the switch, K is a constant which depends on the load and the configuration of the converter, and Vrms is the input rms average. "Vout" is derived from "td", and this equation can be used to calculate a most efficient turn-on time. Therefore, both the peak current and the zero current of the inductor 414 are detected by the inductor current detection unit 422, and the peak current and the zero current are sent to the operation unit 423 to calculate “td”, and then derive “Vout”. Then the calculated “Vout” is sent from the calculation unit 423 to the switch conduction time unit 424 . If the output voltage is lower than expected, the switch will be on longer to boost the output voltage. If the output voltage is greater than the expected voltage, the switch on time will be shortened to prevent the output voltage from rising further.

Please refer to Figure 5, Figure 5(a) shows the relative relationship between the change of inductor current IL and time t, where the vertical axis represents the detected inductor current IL, and the horizontal axis represents time t, where "ton" on the horizontal axis is the time elapsed for the switch to turn on, and "td" is the time elapsed for the energy transfer diode to be turned on, the inductor current can always be detected during "td" and "ton" (such as the solid line part of the triangle), And the zero value and peak current of the inductor can be measured at the same time. Figure 5(b) shows the relative relationship between switch current and time change, where the vertical axis represents the detected switch current, and the horizontal axis represents time, where "ton" on the horizontal axis is the time elapsed for the switch to turn on, and the switch The current measured during the turn-on time is shown by the dotted line of the triangle. Figure 5(c) shows the relative relationship between diode current and time, where the vertical axis represents the detected diode current, and the horizontal axis represents time, where "td" on the horizontal axis is the time elapsed for the energy transfer diode to turn on Time, the current measured by the diode at the turn-on time is shown by the dotted line of the triangle.

As shown in Figure 5(a), (b) and (c) above, "ton" is the time from detecting the zero value current of the inductor to the peak current, that is, the time from detecting the zero value current of the switch to the peak current , "td" is the time from detecting the peak current of the inductor to the zero value current, that is, the time from detecting the peak current of the switch to detecting the zero current of the inductor. Therefore, the detection of this "td" does not actually require additional equipment. It can be deduced that after processing this "td" with the output signal from the AC voltage detection unit, "Vout" can be derived according to the aforementioned relational expression.

In summary, in the first embodiment, both the zero-value current and the peak current of the inductor can be detected. In the second embodiment, both the inductor zero current and the switch peak current can also be detected. Therefore, no matter in any case, "td" and "ton" are known, so "Vout" can be derived without detecting the voltage of the output stage of the load.

Claims (12)

1. Switching Power Supply, it provides output voltage based on input voltage, and described Switching Power Supply comprises:

Boost converter, it promotes the level of described output voltage based on inductive current inside, alternating voltage and switching current; And

Power factor correcting controller, it is coupled to described boost converter and comprises:

The switching current detecting unit, it detects described switching current, so that reference potential to be provided;

Arithmetic element, it carries out computing to the described switching current that described inductive current, described alternating voltage and described switching current detecting unit are detected, so that current potential to be measured to be provided; And

Comparator, the current potential described to be measured that described switching current reference potential that it is detected described switching current detecting unit and described arithmetic element are provided compares, and so that reset signal to be provided, described boost converter is moved according to described reset signal.

2. Switching Power Supply as claimed in claim 1, wherein said input voltage is a civil power.

3. Switching Power Supply as claimed in claim 1, wherein said boost converter further comprises EMI protection circuit, rectifier, energy storage device and output stage.

4. Switching Power Supply as claimed in claim 3, wherein said rectifier is a full wave bridge rectifier.

5. Switching Power Supply as claimed in claim 3, wherein said energy storage device comprises:

Inductor, it passes through for described inductive current;

Switch, it has input, control end and output, and described input is coupled to described inductor, and described control end is controlled by described reset signal;

Resistance, it is coupled to the described output of described switch, so that described switching current to be provided; And

Diode, it is coupled to the described input of described inductor and described switch.

6. Switching Power Supply as claimed in claim 5, wherein said switch is a transistor.

7. Switching Power Supply as claimed in claim 3, wherein said output stage comprises:

Filter capacitor, it is parallel to described energy storage device; And

Output loading, it is parallel to described filter capacitor, so that described output voltage to be provided.

8. Switching Power Supply as claimed in claim 1, wherein said power factor correcting controller further comprises:

The inductive current detecting unit, it is coupled to described boost converter, detects described inductive current and it is provided to described arithmetic element;

The alternating voltage detecting unit, it is coupled to described boost converter, detects described alternating voltage and it is provided to described arithmetic element; And

Switch control unit, it is coupled to described boost converter, and receives described reset signal, to control the operation of described boost converter.

9. Switching Power Supply as claimed in claim 8, wherein said inductive current detecting unit further provides signalization to described switch control unit according to described inductive current, with the operation of the described boost converter of further control.

10. Switching Power Supply, it provides output voltage based on input voltage, and described Switching Power Supply comprises:

Boost converter, it is based on inductive current inside and alternating voltage and promote the level of described output voltage; And

Power factor correcting controller, it is coupled to described boost converter and comprises:

Arithmetic element, it carries out computing to described inductive current and described alternating voltage, so that reset signal to be provided; And

The switch conduction time quantum, its reception also transmits described reset signal, so that described boost converter moves according to described reset signal.

11. Switching Power Supply as claimed in claim 10, wherein said boost converter further comprises EMI protection circuit, rectifier, energy storage device and output stage.

12. Switching Power Supply as claimed in claim 11, wherein said energy storage device comprises:

Inductor, it passes through for described inductive current;

Switch, it has input, control end and output, and described input is coupled to described inductor, and described control end is controlled by described reset signal; And

Diode, it is coupled to the described input of described inductor and described switch.

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