TWI509967B - Switching regulator and control circuit and control method thereof - Google Patents

Description

Switching power supply and control circuit and control method thereof

The invention relates to a switching power supply and a control circuit and a control method thereof, in particular to a switching power supply for improving Total Harmonic Distortion (THD), a control circuit thereof and a control method thereof.

Figure 1A shows a schematic diagram of a typical isolated switched power supply 100. As shown in FIG. 1A, the to-be-rectified voltage Vac is, for example, a direct current or an alternating current voltage, and is rectified by the rectifier circuit 101 to generate an input voltage Vin. The rectifier circuit 101 is, for example, a bridge rectifier circuit. The isolated power converter circuit 100 utilizes the transformer circuit 102 therein to receive the input voltage Vin for conversion to the output voltage Vout. The isolated switching power supply 100 includes the foregoing transformer circuit 102, power switch 103, control circuit 105, current sensing circuit 106, and voltage sensing circuit 107. The control circuit 105 generates a driving signal GATE according to the current sensing signal CS generated by the current sensing circuit 106 and the feedback signal FB generated by the voltage sensing circuit 107 to convert the input voltage Vin into an output voltage Vout. The transformer circuit 102 includes a first winding W1, a second winding W2, and a third winding W3. The second winding is coupled to the ground potential, and the first winding W1 and the third winding W3 are commonly coupled to the reference potential, and the voltage sensing circuit 107 senses the output voltage Vout generated by the second winding W2 according to the third winding W3. The feedback signal FB.

FIG. 1B shows a schematic diagram of another isolated power converter circuit 200. The control circuit 205 generates a driving signal GATE according to the current sensing signal CS and the feedback signal FB generated by the current sensing circuit 106 to convert the input voltage Vin into an output voltage Vout. However, the difference from the prior art shown in FIG. 1A is that the voltage sensing circuit 207 is coupled to the transformer. The output terminal of the second winding W2 of the circuit 202 directly senses the output voltage Vout, and the optical sensing circuit 204 is used to optically convert the result of the sensing voltage Vout by the voltage sensing circuit 207 into a feedback signal FB, and the input is controlled. Circuit 205.

The foregoing typical isolated switching power supplies 100 and 200 have a total harmonic distortion (THD) problem. To improve total harmonic distortion (THD) and improve power conversion efficiency, the present invention proposes an improved total harmonic distortion switching. Power supply and its control circuit and control method.

In one aspect, the present invention provides a switched power supply for converting an input voltage into an output voltage, the switched power supply comprising: a power stage circuit for switching at least one of the driving signals according to a driving signal a power switch for converting an input voltage into an output voltage; and a control circuit coupled to the power stage circuit, the control circuit comprising: a PWM circuit for generating a PWM signal according to a feedback signal; and a shaping weighting a circuit coupled to the PWM circuit to receive the PWM signal, and delaying a period of a rising edge or a falling edge of each period of the PWM signal according to the input voltage The preset time, which in turn generates the drive signal.

In another aspect, the present invention provides a control circuit for a switched power supply, wherein the switched power supply is configured to convert an input voltage into an output voltage, including a power stage circuit, and switch at least according to a driving signal. a power switch for converting an input voltage into an output voltage, the control circuit comprising: a PWM circuit for generating a PWM signal according to a feedback signal; and a shaping weighting circuit coupled to the PWM circuit for receiving The PWM signal is delayed according to the input voltage by a predetermined time when a rising edge or a falling edge of each period of the PWM signal occurs, thereby generating the driving signal.

In a preferred embodiment, the preset time is extended when the input voltage rises and shortened when the input voltage drops.

In the foregoing embodiment, the preset time may be proportional to the input voltage or the input voltage variation.

In a preferred embodiment, the power stage circuit includes a transformer circuit.

In a preferred embodiment, the shaping weighting circuit includes: a ramp generating circuit for generating a ramp, the ramp generating circuit receiving the PWM signal as a clock, and the slope generated by the ramp generating circuit is related to a reciprocal of the input voltage; and a quasi-comparator that compares the slope generated by the ramp generating circuit with a reference level and generates the driving signal according to the comparison result.

In a preferred embodiment, the shaping weighting circuit includes: a ramp generating circuit for generating a ramp, the ramp generating circuit receiving the PWM signal as a clock; and a quasi comparator for generating the ramp The slope generated by the circuit is compared with the proportional value of the input voltage, and the driving signal is generated according to the comparison result.

In another aspect, the present invention provides a switching power supply control method, wherein the switching power supply is configured to convert an input voltage into an output voltage, including a power stage circuit, and switch at least according to a driving signal. a power switch for converting an input voltage into an output voltage, wherein the switching power supply control method comprises: generating a PWM signal according to a feedback signal; and receiving the PWM signal, and according to the input voltage, In the PWM signal, the rising edge or the falling edge of each period is delayed by a predetermined time to generate the driving signal.

In a preferred embodiment, the preset time is extended when the input voltage rises and shortened when the input voltage drops.

In the foregoing implementation manner, the preset time may be proportional to the input voltage or The amount of input voltage change.

The purpose, technical content, features and effects achieved by the present invention will be more readily understood by the detailed description of the embodiments.

100,200‧‧‧Isolated switched power supply

101‧‧‧Rectifier circuit

102,202‧‧‧Transformer circuit

103‧‧‧Power switch

105,205‧‧‧Control circuit

106‧‧‧ Current sensing circuit

107‧‧‧Voltage sensing circuit

204‧‧‧Optocoupler circuit

300‧‧‧Switching power supply

302‧‧‧Power level circuit

303‧‧‧Power switch

305‧‧‧Control circuit

3051‧‧‧PWM circuit

3053‧‧‧Shaping weighting circuit

CS‧‧‧current sensing signal

Cs1‧‧‧Charging current source

Cs2‧‧‧Discharge current source

C1‧‧‧ capacitor

FB‧‧‧ feedback signal

I, I1, I2‧‧‧ current

N1, N2, N3, N4, N5‧‧‧ Inverting components

PWM1‧‧‧PWM signal

PWM2‧‧‧ drive signal

Q‧‧‧output

Q1, Q2‧‧‧ switch

R‧‧‧Reset end

S‧‧‧Setting end

Tdelay1, Tdelay2‧‧‧Preset time

Vac‧‧‧ to be rectified voltage

Vin‧‧‧Input voltage

Vout‧‧‧ output voltage

W1‧‧‧First winding

W2‧‧‧second winding

W3‧‧‧ third winding

Figure 1A shows a schematic diagram of a typical isolated switched power supply 100.

FIG. 1B shows a schematic diagram of another isolated power converter circuit 200.

Fig. 2A-2C shows a first embodiment of the present invention.

Figure 3A-3J shows a synchronous or non-synchronous step-down, step-up, back-pressure, buck-boost, and step-up power stage circuit.

Figure 4 is a diagram showing the signal waveforms of the input voltage Vin and the preset delay time Tdelay according to the present invention.

Figure 5 shows a second embodiment of the invention.

Figures 6A-6C show third, fourth, and fifth embodiments of the present invention.

Referring to Figures 2A-2C, a first embodiment of the present invention is shown. As shown in FIG. 2A, the switched power supply 300 includes a power stage circuit 302 and a control circuit 305. The power stage circuit 302 switches the power switch 303 to convert the input voltage Vin to the output voltage Vout according to a driving signal GATE. The control circuit 305 is coupled to the power stage circuit 302 and includes a pulse width modulation (PWM) circuit 3051 and a shaping weighting circuit 3053. The PWM circuit 3051 generates a PWM signal PWM1 according to the feedback signal FB. The feedback signal FB is associated with the output voltage Vout, for example, from the output of the power stage circuit 302, or from the output voltage Vout, or when the power stage circuit 302 is an isolated power conversion circuit using a transformer, the self-assisted winding Obtained. Shaped weighted electricity The circuit 3053 is coupled to the PWM circuit 3051 to receive the PWM signal PWM1, and delays a period of a rising edge or a falling edge of each period of the PWM signal PWM1 according to the input voltage Vin. The preset time Tdelay1 or Tdelay2, as shown in Figures 2B and 2C, generates a drive signal PWM2. As shown in FIGS. 2B and 2C, the PWM circuit 3051 generates the PWM signal PWM1 and inputs it into the shaping weighting circuit 3053. Referring to FIG. 2B, the shaping weighting circuit 3053 delays the rising edge of each period of the PWM signal PWM1 by a predetermined time Tdelay1 to generate the driving signal PWM2. Referring to FIG. 2C, the shaping weighting circuit 3053 delays the time when the falling edge of each period of the PWM signal PWM1 occurs by a predetermined time Tdelay2 to generate the driving signal PWM2. The power stage circuit 302 can be a synchronous or non-synchronous buck, boost, back pressure, or buck-boost type, in addition to the isolated switching power supply shown in FIGS. 1A and 1B. The power stage circuit is shown in Figure 3A-3J. As shown in Figures 1A and 1B, isolated switched power supplies 100 and 200 include transformer circuits 102 and 202.

Figure 4 is a diagram showing the signal waveforms of the input voltage Vin and the preset delay time Tdelay according to the present invention. As shown in the figure, the preset time Tdelay is extended when the input voltage Vin rises, and is shortened when the input voltage Vin falls. A preferred embodiment is to set the preset time Tdelay to be proportional to the input voltage Vin, or proportional to the amount of change ΔVin of the input voltage per unit time (ie, the voltage difference between the current time and the previous time).

Figure 5 shows a second embodiment of the invention. This embodiment shows a more specific embodiment of the shaping weighting circuit 3053. In the present embodiment, the shaping weighting circuit 3053 generates a driving signal PWM2 by delaying a predetermined time Tdelay1, for example, but not limited to, the time point at which the rising edge of each period in the PWM signal PWM1 is delayed. Figure 5 shows that the shaping weighting circuit 3053 includes inverting elements N1, N2, N3 and N4, switches Q1 and Q2, a charging current source Cs1, and a capacitor C1, wherein the switches Q1 and Q2, the charging current source Cs1, and the capacitor C1 constitute The ramp generates a circuit, and the clock of the ramp generates the circuit by the PWM signal PWM1 determines, and the current I of the charging current source Cs1 is proportional to the reciprocal of the input voltage Vin. The purpose of the inverting components N1, N2 is to maintain the duty ratio of the PWM signal PWM1, but change the absolute value of its high and low levels to meet the operation of the switches Q1 and Q2. If the level of the PWM signal PWM1 itself is appropriate, the inverting elements N1, N2 may not be needed in the circuit. The charging current source circuit Cs1 generates a current I, and the current I is proportional to the reciprocal of the input voltage Vin; the switching of the switches Q1 and Q2 is controlled by the working ratio of the PWM signal PWM1, and the charging and discharging of the controlling capacitor C1 is controlled by the switching of the switches Q1 and Q2. The voltage of the capacitor C1 (ie, the ramp generated by the ramp generating circuit) is related to the reciprocal of the input voltage Vin, and then the driving signal PWM2 is generated via the inverting elements N3 and N4, thereby generating a delay effect. In detail, since the current I is proportional to the reciprocal of the input voltage Vin, the higher the input voltage Vin, the smaller the current I, the slower the charging speed of the capacitor C1, and the slower the level change point to the inverting element N3. That is, the delay time is proportional to the input voltage Vin. In this embodiment, the comparators may also be used to replace the inverting elements N3 and N4, one end of the comparator receives the voltage of the capacitor C1, and the other end receives a reference voltage (corresponding to the level change point of the inverting element N3); or Instead of the inverting elements N3 and N4, a Smith trigger is used. Inverting components, comparators, or Smith flip-flops all have a level-comparison effect and can be considered a form of a level comparator.

In fact, according to the basic physical formula, the product of the capacitance value (C) and the voltage (V) is equal to the product of the current (i) and the time (t) (CV = it), so if the delay time is to be changed and the delay time is proportional to The input voltage Vin can be varied in addition to the current I in the manner of the embodiment of Fig. 5. FIG. 6A shows a third embodiment of the present invention. This embodiment shows another more specific embodiment of the shaping weighting circuit 3053, similar to the second embodiment of FIG. 5, but the current I of the charging current source Cs1. The value is fixed, and the shaping weighting circuit 3053 includes a comparator Comp1, which compares the voltage of the capacitor C1 with the correlation value Vin/R of the input voltage Vin, where R can be a desired proportional value. The correlation value Vin/R can be taken, for example, from the partial pressure of the input voltage Vin. In this embodiment, the PWM signal can also be made. When the PWM2 changes from the low level to the high level, the delay time is proportional to the input voltage Vin compared to the time when the PWM signal PWM1 changes from the low level to the high level.

The ramp generating circuit in FIGS. 5 and 6A is a rising waveform ramp generating circuit; the present invention is not limited thereto, and other types of ramp generating circuits, such as the falling waveform ramp generating circuit shown in FIG. 6B, or It is a ramp generating circuit having a rising and falling waveform shown in FIG. 6C, wherein Cs2 is a discharging current source. In the sixth embodiment, the charging current source Cs1 generates a charging current I1, and the discharging current source Cs2 generates a charging current I2. Both can be equal or unequal. When the ramp generating circuit shown in FIG. 6B or FIG. 6C is used, it is possible to change the input terminal connection mode of the comparator Comp1 as needed.

In addition, it is obvious that if the PWM signal PWM1 is delayed from the high level to the low level, the reverse signal of the PWM signal PWM1 can be used to control the clock of the ramp generating circuit in the above-exemplified circuit.

It should be noted that according to the present invention, Total Harmonic Distortion (THD) and Electro-magnetic interference (EMI) can be improved, and a quasi-resonant (QR) switching power supply is provided. The effect of the device. The operation mode to which the present invention is applied is preferably applied to a boundary conduction mode (BCM), which is a technique commonly used in the technical field, and is not described herein. Compared with the typical quasi-resonant switching power supply, the circuit of the invention is simpler and the operation mode is simpler, which is superior to the prior art in the invention. Taking a typical quasi-resonant switching power supply as an example, the prior art must continuously detect the turning point of the high and low levels in the output signal, and the circuit and operation mode are relatively complicated, and the manufacturing cost is also high.

The present invention has been described with reference to the preferred embodiments thereof, and the present invention is not intended to limit the scope of the present invention. In the same spirit of the invention, various equivalent changes can be conceived by those skilled in the art. For example, in the various embodiments, two circuits or elements that are directly connected may be interposed, and other circuits or elements that do not affect the main function may be interposed. All of these can be according to the invention The teachings are analogous and, therefore, the scope of the invention is intended to cover the above and other equivalents.

300‧‧‧Switching power supply

302‧‧‧Power level circuit

303‧‧‧Power switch

305‧‧‧Control circuit

3051‧‧‧PWM circuit

3053‧‧‧Shaping weighting circuit

FB‧‧‧ feedback signal

PWM1‧‧‧PWM signal

PWM2‧‧‧ drive signal

Claims (10)

A switching power supply for converting an input voltage into an output voltage, the switching power supply comprising: a power stage circuit, switching at least one of the power switches to convert the input voltage into an output voltage according to a driving signal And a control circuit coupled to the power stage circuit, the control circuit comprising: a pulse width modulation (PWM) circuit for generating a PWM signal according to a feedback signal; and a shaping weighting a circuit coupled to the PWM circuit to receive the PWM signal, and delaying a period of a rising edge or a falling edge of each period of the PWM signal according to the input voltage The preset time further generates the driving signal; wherein the preset time is extended when the input voltage rises and shortened when the input voltage drops. The switching power supply of claim 1, wherein the preset time is proportional to the input voltage or proportional to the amount of change of the input voltage per unit time. A switching power supply for converting an input voltage into an output voltage, the switching power supply comprising: a power stage circuit, switching at least one of the power switches to convert the input voltage into an output voltage according to a driving signal And a control circuit coupled to the power stage circuit, the control circuit comprising: a pulse width modulation (PWM) circuit for generating a PWM signal according to a feedback signal; and a shaping weighting a circuit coupled to the PWM circuit to receive the PWM signal, and delaying a period of a rising edge or a falling edge of each period of the PWM signal according to the input voltage Preset And the generating of the driving signal; wherein the shaping weighting circuit comprises: a ramp generating circuit for generating a ramp, the ramp generating circuit receiving the PWM signal as a clock, and the slope generated by the ramp generating circuit is related to a reciprocal of the input voltage; and a quasi-comparator that compares the slope generated by the ramp generating circuit with a reference level and generates the driving signal according to the comparison result. A switching power supply for converting an input voltage into an output voltage, the switching power supply comprising: a power stage circuit, switching at least one of the power switches to convert the input voltage into an output voltage according to a driving signal And a control circuit coupled to the power stage circuit, the control circuit comprising: a pulse width modulation (PWM) circuit for generating a PWM signal according to a feedback signal; and a shaping weighting a circuit coupled to the PWM circuit to receive the PWM signal, and delaying a period of a rising edge or a falling edge of each period of the PWM signal according to the input voltage Presetting the time to generate the driving signal; wherein the shaping weighting circuit comprises: a ramp generating circuit for generating a ramp, the ramp generating circuit receiving the PWM signal as a clock; and a quasi comparator The slope generated by the ramp generating circuit is compared with the proportional value of the input voltage, and the driving signal is generated according to the comparison result. A switching power supply control circuit, wherein the switching power supply is configured to convert an input voltage into an output voltage, comprising a power stage circuit, switching at least one of the power switches to convert the input voltage into an output according to a driving signal Voltage, the control circuit comprises: a PWM circuit, according to a feedback signal, to generate a PWM signal; and a shaping weighting circuit coupled to the PWM circuit to receive the PWM signal, and according to the input voltage, the PWM signal The rising edge or the falling edge of the period is delayed for a predetermined period of time to generate the driving signal; wherein the preset time is extended when the input voltage rises, when the input voltage drops shorten. The control circuit of the switching power supply according to claim 5, wherein the preset time is proportional to the input voltage or the input voltage variation. A switching power supply control circuit, wherein the switching power supply is configured to convert an input voltage into an output voltage, comprising a power stage circuit, switching at least one of the power switches to convert the input voltage into an output according to a driving signal Voltage, the control circuit includes: a PWM circuit, according to a feedback signal, to generate a PWM signal; and a shaping weighting circuit coupled to the PWM circuit to receive the PWM signal, and according to the input voltage, In the PWM signal, a rising edge or a falling edge of each period is delayed by a predetermined time to generate the driving signal; wherein the shaping weighting circuit comprises: a ramp generating a circuit for generating a ramp, the ramp generating circuit receiving the PWM signal as a clock, and a ramp generated by the ramp generating circuit is related to a reciprocal of the input voltage; and a quasi-comparator for the ramp generating circuit The generated ramp is compared with a reference level and the aforementioned drive signal is generated based on the comparison result. A switching power supply control circuit, wherein the switching power supply is configured to convert an input voltage into an output voltage, comprising a power stage circuit, switching at least one of the power switches to convert the input voltage into an output according to a driving signal Voltage, the control circuit comprises: a PWM circuit, according to a feedback signal, to generate a PWM signal; and a shaping weighting circuit coupled to the PWM circuit to receive the PWM signal, and according to the input voltage, the PWM signal a time when a rising edge or a falling edge occurs, delaying for a predetermined period of time to generate the driving signal; wherein the shaping weighting circuit comprises: a ramp generating circuit for generating a slope, The ramp generating circuit receives the PWM signal as a clock; and a quasi-comparator compares the slope generated by the ramp generating circuit with a proportional value of the input voltage, and generates the driving signal according to the comparison result. A switching power supply control method, wherein the switching power supply is configured to convert an input voltage into an output voltage, comprising a power stage circuit, switching at least one of the power switches to convert the input voltage into an output according to a driving signal Voltage, the switching power supply control method comprises: generating a PWM signal according to a feedback signal; and receiving the PWM signal, and according to the input voltage, the rising edge of the PWM signal A rising edge or a falling edge occurs for a predetermined period of time to generate the driving signal; wherein the predetermined time is extended when the input voltage rises and shortened when the input voltage drops. The control method of the switching power supply device of claim 9, wherein the preset time is proportional to the input voltage or proportional to the amount of change of the input voltage per unit time.