CN103856058A - Voltage conversion circuit and voltage conversion controller - Google Patents

Abstract

The present invention relates to a voltage conversion circuit, comprising an application circuit and a voltage conversion controller. The application circuit comprises an output terminal, a feedback terminal and a feedback capacitor coupled to the feedback terminal. The output terminal has an output voltage and is coupled to a current load. The voltage conversion controller has a feedback terminal pin coupled to the feedback terminal. The voltage conversion controller has a first mode and a second mode. In the first mode, the output terminal provides a regulated output voltage and supplies current to the current load, and the feedback terminal pin receives a feedback signal. In the second mode, the output voltage is not regulated, and the feedback terminal pin provides a fixed periodic counting frequency signal, and the period size of the counting frequency signal is determined by the capacitance value of the feedback capacitor.

Description

Voltage conversion circuit and voltage conversion controller

【Technical field】

The present invention relates to a voltage conversion circuit, in particular to a voltage conversion circuit including a multi-functional single-pin voltage conversion controller.

【Background technique】

Please refer to US Patent No. US7,848,124. The voltage conversion controller is applied in a fly-back switching power converter. The flyback switching power converter is a kind of voltage conversion circuit configuration, and its purpose is to provide a stable output voltage. When the flyback switching power supply conversion circuit is in steady-state operation, the voltage conversion controller regulates its output voltage through negative feedback control to provide a stable and rated output voltage value and output The current is given to a current load. At this time, there is a signal on the feedback point IN3 on the negative feedback control path, which is a signal linearly related to the magnitude of its output current, and the voltage conversion controller performs negative feedback according to the signal on the feedback point IN3 control. And when the flyback switching power supply conversion circuit is in an unsteady state operation, for example, when the load current is too large and the load current is too large to protect the operation, or the soft start operation of the initial startup of the circuit, the rated output voltage at this time The value has not been established, and because the signal on the feedback point IN3 is related to the signal at the output terminal, the signal on the feedback point IN3 at this time is finally a continuous DC voltage signal after experiencing a short transient response, and for Circuit operation does not provide a function of substantial benefit.

In the current mainstream applications, the voltage conversion controller is usually implemented by an integrated circuit, and cooperates with an external application circuit to form a voltage conversion circuit, so as to optimize cost, circuit size, and flexibility of use. The integrated circuit includes pins that are electrically connected to external electronic components. In order to optimize cost and volume, the number of pins of the integrated circuit can be as few as possible without affecting the flexibility of use. Therefore, in terms of design, if the pins can provide functions with substantial benefits under all circuit usage states, it is the optimal use of the pins. Taking the previous technology as an example above, the pin representing the feedback point does not provide a function that has substantial benefits for the circuit operation when the voltage conversion controller is in an unsteady state. This is the current integration of general voltage conversion controllers. common phenomenon in circuits.

【Content of invention】

In view of this, the present invention provides a voltage conversion circuit, which includes a voltage conversion controller, which is an integrated circuit, and the voltage conversion controller can provide a single pin with multiple functions, so as to optimize the utilization of the pins.

The voltage conversion circuit disclosed in the present invention includes an application circuit and a voltage conversion controller. The application circuit includes an output terminal, a feedback terminal and a feedback capacitor coupled to the feedback terminal. The output terminal has an output voltage and is coupled to a current load. The voltage conversion controller has a feedback terminal pin coupled to the feedback terminal. The voltage conversion controller has a first mode and a second mode. In the first mode, the output terminal provides a regulated output voltage and supplies current to a current load, and the feedback terminal pin receives a feedback signal. In the second mode, the output voltage is not adjusted, and the feedback terminal pin provides a counting frequency signal with a fixed period, and the period of the counting frequency signal is determined by the capacitance value of the feedback capacitor.

The effect of the present invention is that the technical features disclosed in the present invention can save the use of integrated circuit pins, thereby further saving costs; and the voltage conversion controller of the same design can be used in various applications, thereby reducing integration The number of versions of circuit components derived from various applications simplifies production, inventory, and management issues for manufacturers.

Regarding the features, implementation and effects of the present invention, the preferred embodiments are described in detail below in conjunction with the drawings.

【Description of drawings】

FIG. 1 is a schematic circuit diagram of a voltage converter of the present invention.

FIG. 2 is a schematic functional block diagram of the voltage conversion controller of the present invention.

FIG. 3 is a schematic diagram of the voltage waveforms of each main terminal when the voltage conversion controller of the present invention performs a soft start operation.

FIG. 4 is a schematic diagram of a voltage waveform in a partially enlarged region in FIG. 3 .

FIG. 5 is a schematic diagram of the voltage waveforms of each main terminal when the voltage conversion controller of the present invention performs an output overcurrent protection operation.

FIG. 6 is a schematic circuit diagram of an oscillation controller among the voltage conversion controllers of the present invention.

Description of main component symbols:

100 Voltage Converter 151 Light Sensing Component

110 power supply unit 243 second current switch

111 Bridge full-wave rectifier 244 Second current component

112 Input Stabilizing Capacitor 245 Internal Voltage Source

113 primary side coil 251 counter

130 Output unit 252 Soft start control circuit

131 Secondary coil 253 Overload protection control circuit

132 Output diode 254 Shutdown logic circuit

133 Output Stabilizer Capacitor 255 Oscillation Controller

134 The first feedback resistor 280 Charge and discharge circuit

135 Second feedback resistor 310 Output voltage waveform

136 Current limiting resistor 320 Output waveform of oscillation controller

137 Light-emitting diode 330 Voltage waveform of the feedback terminal pin

138 Three-terminal shunt regulator 331 The first comparison voltage value of the oscillation controller

150 Feedback circuit unit 332 The second comparison voltage value of the oscillation controller

340 The output waveform of the current-limiting control stage 242 The first current switch

341 The voltage value of the equivalent current-limiting control stage for steady-state operation

The voltage waveform of the sense voltage pin under 350

152 feedback capacitor 360 340 and 350 partially amplified waveform area

170 Power switch unit 510 Output waveform of overload protection control circuit

171 Power switch 520 Oscillation controller output waveform

172 Current sense resistor 530 Voltage waveform of feedback terminal pin

200 Voltage conversion controller 531 The first comparison voltage value of the oscillation controller

210 Power switch control pin 532 The second comparison voltage value of the oscillation controller

211 Power switch driving stage 540 Output waveform of current limiting control stage

212 Pulse Width Modulation Latch 550 Voltage Waveform of Current Sense Voltage Pin

213 Internal Oscillator 610 Controller Input

214 PWM comparator 620 Controller output terminal

215 current limit control stage 630 first comparator

220 current sense voltage pin 640 second comparator

221 Gain stage 650 First comparison voltage

230 ground pin 660 second comparison voltage

240 Feedback Pin 670 Set Reset Latch

241 The first current component

【Detailed ways】

In the description and the scope of subsequent patent applications, the term "coupling" here includes any direct and indirect electrical connection means. Therefore, if it is described in the text that a first device is coupled to a second device, it means that the first device may be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices or connection means. Two devices.

FIG. 1 is a schematic circuit diagram of a voltage conversion circuit 100 . The voltage conversion circuit 100 is configured as a flyback switching power conversion circuit. The voltage conversion circuit 100 includes the voltage conversion controller 200 of the present invention and an application circuit. The application circuit includes an output terminal and a feedback terminal COMP. The output terminal has an output voltage and is coupled to a current load. The voltage conversion controller 200 further includes a power supply unit 110 , an output unit 130 , a feedback circuit unit 150 and a power switch unit 170 .

As shown in FIG. 1 , the power supply unit 110 includes a bridge full-wave rectifier 111 , an input voltage stabilizing capacitor 112 , and a primary coil 113 .

The bridge full-wave rectifier 111 performs full-wave rectification on an input AC power VAC and provides a full-wave rectification result at its output.

The input stabilizing capacitor 112 is coupled to the output of the bridge full-wave rectifier 111 , and stabilizes the full-wave rectified result to generate an input voltage VIN on the input stabilizing capacitor 112 .

The primary side coil 113 has a first terminal and a second terminal, and the first terminal is coupled to the input stabilizing capacitor 112 . The main function of the power supply unit 110 is to provide the input voltage VIN to the primary coil 113 .

As shown in FIG. 1 , the output unit 130 includes a secondary side coil 131, an output diode 132, an output voltage stabilizing capacitor 133, a first feedback resistor 134, a second feedback resistor 135, and a current limiting resistor. 136 , a light emitting diode 137 , and a three-terminal shunt regulator 138 .

The secondary coil 131 has a first terminal and a second terminal, and has a mutual inductance relationship with the primary coil 113 to form a transformer assembly.

The anode terminal of the output diode 132 is coupled to the first terminal of the secondary coil 131 . The negative end of the output diode 132 is coupled to one end of the output voltage stabilizing capacitor 133 to form a positive output end VOP.

The other terminal of the output voltage stabilizing capacitor 133 is coupled to the second terminal of the secondary side coil 131 and forms a negative terminal VON of an output terminal. An output voltage is provided between the positive terminal VOP of the output terminal and the negative terminal VON of the output terminal.

The first feedback resistor 134 is coupled between the positive terminal VOP of the output terminal and one end of the second feedback resistor 135 . The other end of the second feedback resistor 135 is coupled to the negative end VON of the output end. The connection point of the first feedback resistor 134 and the second feedback resistor 135 provides an output voltage divider VFB, and is coupled to the input terminal of the three-terminal shunt regulator 138 .

One terminal of the current limiting resistor 136 is coupled to the positive terminal VOP of the output terminal, and the other terminal is coupled to the positive terminal of the LED 137 .

The negative terminal of the LED 137 is coupled to the positive output terminal of the three-terminal shunt regulator 138 . The negative output terminal of the three-terminal shunt regulator 138 is coupled to the negative terminal VON of the output terminal.

As shown in Figure 1, the three-terminal shunt regulator 138 includes a reference voltage value, and when the voltage at the input terminal is greater than the reference voltage value, there is a lead between the output positive terminal and the output negative terminal of the three-terminal shunt regulator 138. pass status. Conversely, when the voltage at its input terminal is lower than the reference voltage value, the positive output terminal and the negative output terminal of the three-terminal shunt regulator 138 are in a non-conductive state. Therefore, when the output voltage divided voltage VFB is greater than the reference voltage value, the output of the three-terminal shunt regulator 138 is turned on, and a current is formed on the light-emitting diode 137, and the magnitude of the current is limited by the current limiting resistor 136. At this time The light emitting diode 137 forms a luminescent light source; and when the output voltage divided voltage VFB is less than the reference voltage value, the output of the three-terminal shunt regulator 138 is not conducted, and there is no current on the light emitting diode 137, that is, the light emitting diode 137 does not glow.

As shown in FIG. 1 , the power switch unit 170 includes a power switch 171 and a current sensing resistor 172 . The output of the power switch 171 is connected in series with the sense resistor 172 and coupled between the second terminal of the primary coil 113 and the ground terminal. When the power switch 171 is turned on, the input voltage stabilizing capacitor 112 , the primary side coil 113 , the power switch 171 and the current sensing resistor 172 form a current loop. Since the primary coil 113 is an inductive component, the formation of the current loop will store energy on the primary coil 113 . In addition, the sense resistor 172 converts the current signal on the current loop into a voltage signal VCS. When the power switch 171 is turned off, the stored energy on the primary side coil 113 passes through the transformer assembly formed with the secondary side coil 131 and is released to the secondary side coil 131 to form a current on it, and the voltage conversion circuit 100 is in a steady state. In normal operation, a rated output voltage VOUT is established between the positive terminal and the negative terminal of the output terminal, and a current is provided to a current load (not shown) connected in series between the positive terminal and the negative terminal of the output terminal.

As shown in FIG. 1 , the feedback circuit unit 150 includes a light sensing element 151 and a feedback capacitor 152 . The photo-sensing element 151 and the light-emitting diode 137 form an optical coupler configuration. When the light-emitting diode 137 forms a light source, the light-sensing element 151 detects the light source and forms a current on it, and the resulting The magnitude of the current is directly proportional to the intensity of the light source. It can be seen that, by using the transformer and the optocoupler, the side of the input AC power supply and the side of the output terminal can be completely electrically isolated.

As shown in FIG. 1 , the light sensing component 151 is connected in parallel with the feedback capacitor 152 and is coupled between the feedback terminal COMP and the ground terminal of the application circuit. The voltage conversion controller 200 is an integrated circuit unit and has a plurality of pins. The pins include a power switch control pin 210 , a sense voltage pin 220 , a ground pin 230 and a feedback terminal pin 240 . The power switch control pin 210 is coupled to the control terminal of the power switch 171 to control the power switch 171 to be turned on and off. The sense voltage pin 220 receives the voltage signal VCS generated by the sense resistor 172 . The ground pin 230 is coupled to the ground terminal. The feedback terminal pin 240 is coupled to the feedback terminal COMP.

FIG. 2 is a schematic functional block diagram of the voltage conversion controller 200 . The voltage conversion controller 200 further includes a first current component 241, a first current switch 242, a second current switch 243, a second current component 244, an internal voltage source 245, a counter 251, and a soft-start control circuit 252, an overload protection control circuit 253, a shutdown logic circuit 254, an oscillation controller 255, a power switch drive stage 211, a pulse width modulation latch 212, an internal oscillator 213, a pulse width modulation comparison device 214, a current limit control stage 215, and a gain stage 221.

The first current component 241 is coupled to the internal voltage source 245 and one end of the first current switch 242 .

The other end of the first current switch 242 is coupled to the feedback pin 240 .

The series connection of the first current component 241 and the first current switch 242 forms a switch current component, wherein the first current component 241 can be a resistor component or a current source component.

The second current component 244 is coupled to the ground pin 230 and one end of the second current switch 243 . The other end of the second current switch 243 is coupled to the feedback pin 240 .

The series connection of the second current component 244 and the second current switch 243 forms another switch current component, wherein the second current component 244 can be a resistor component or a current source component.

The input of the oscillation controller 255 is coupled to the feedback terminal pin 240, and when the voltage conversion circuit 100 operates in an unsteady state, a periodic frequency signal is generated at its output terminal to control the first current switch 242 and the second current switch. 243 on and off.

The output terminal of the oscillation controller 255 is coupled to the counter 251 . The counter 251 outputs a result to the soft-start control circuit 252 and outputs another result to the overload protection control circuit 253 when the voltage conversion circuit 100 operates in an unsteady state.

The overload protection control circuit 253 controls the shutdown logic circuit 254 according to the settings to determine whether to temporarily shut down the voltage conversion controller 200 .

The PWM comparator 214 has a positive input, a first negative input, a second negative input and an output. Its first negative terminal input is coupled to the feedback terminal pin 240 . Its output is coupled to a counter 251 .

The input of the gain stage 221 is coupled to the sense voltage pin 220 , and the output of the gain stage 221 is coupled to the positive input of the PWM comparator 214 . The gain stage 221 outputs the input signal after proper linear amplification. The current-limit control stage 215 provides an equivalent current-limit voltage at its output, and is coupled to the second negative input of the PWM comparator 214 .

The PWM latch 212 has a set input terminal, a reset input terminal and an output terminal. The reset input terminal is coupled to the output of the PWM comparator 214 . The internal oscillator 213 provides a PWM operating frequency and is coupled to the setting input terminal of the PWM latch 212 .

The power switch driving stage 211 has an input terminal and an output terminal, the input terminal is coupled to the output terminal of the pulse width modulation latch 212, the output terminal of the power switch driving stage 211 is coupled to the power switch control pin 210, and The capacitive load at the control end of the power switch 171 is driven according to the input signal at its input end.

The voltage conversion controller 200 cooperates with the application circuit to establish the voltage conversion circuit 100 shown in FIG. 1 . The voltage conversion controller 200 has at least a first mode and a second mode, such as a steady-state operation and an unsteady-state operation. And in the first mode, the feedback terminal pin 240 receives a feedback signal, and in the second mode, the feedback terminal pin 240 provides a counting frequency signal. The feedback signal and the counting frequency signal have different functions in terms of formation and operation.

When the voltage conversion circuit 100 operates in a steady state, the voltage conversion controller 200 feedback controls to adjust the current load between the positive terminal VOP and the negative terminal VON of the output terminal, and provides a regulated rated output voltage VOUT as the output voltage. The so-called regulated person refers to that when the parameters of the external application circuit and the current load change within the specified range, the voltage conversion controller 200 can react with the negative feedback control mechanism established by the external application circuit, so as to Keep the output voltage at a rated VOUT.

When the voltage conversion circuit 100 is in an unsteady state operation, the voltage conversion controller 200 cooperates with the application circuit, and will perform necessary reactions to protect the voltage conversion controller 200, each component in the application circuit, and the current load, so that the application circuit is free from Component damage or other malfunctions due to overvoltage or overcurrent conditions. Common unsteady operation responses include soft start, under-input voltage lockout, over-output over-voltage protection, over-current over-output protection, and more. Embodiments of the present invention will describe the technical features of the steady-state operation of the voltage conversion circuit 100 and the non-steady-state operation of soft start and output overcurrent protection, which are described below.

When the voltage conversion circuit 100 is in steady state operation, the output voltage is a ripple waveform, and the average voltage of the ripple waveform is the rated output voltage VOUT. The periodic behavior of the ripple waveform and the adjustment action of the voltage conversion controller 200 are explained as follows.

At the beginning of the cycle, the internal oscillator 213 of the voltage conversion controller 200 outputs a pulse to trigger the setting input of the PWM latch 212 to generate a signal "1" to trigger the PWM latch 212 At this time, the power switch driving stage 211 drives the control terminal of the power switch 171 to turn on the power switch 171 , and forms a current loop to store energy in the primary side coil 113 . At this time, the transformer does not provide current to the output terminal, so the charge required by the current load on the output terminal comes from the output voltage stabilizing capacitor 133 , so the output voltage drops linearly. And because the current on the primary side coil 113, that is, the current on the power switch 171 continues to rise, so the voltage signal VCS on the sense voltage pin 220 also continues to rise until VCS is greater than the voltage value on the feedback terminal pin 240, thus The frequency width modulation comparator 214 outputs a signal "1" to the reset input terminal of the PWM latch 212 to generate a signal "0" at the output terminal of the PWM latch 212, and the power switch driving stage 211 The power switch 171 is thus turned off. The energy stored on the primary side coil 113 is released to the secondary side coil 131 through the transformer assembly formed with the secondary side coil 131 to form a current on it, thereby providing current to the load current and to the output voltage stabilizing capacitor 133 to charge. At this time, the output voltage rises linearly until the internal oscillator 213 generates a next pulse, and the power switch 171 is turned on. The voltage conversion circuit 100 therefore operates periodically.

When the current value of the load current increases, because the voltage conversion circuit 100 cannot provide enough current for the load current temporarily, the output voltage stabilizing capacitor 133 provides the required extra charge, thereby causing the output voltage to drop. At this time, when the divided voltage VFB of the output voltage is less than the reference voltage of the three-terminal shunt regulator 138, the positive output terminal and the negative output terminal of the three-terminal shunt voltage regulator 138 are not conducting, that is, the output of the light-emitting diode 137 has no current and no light. The light-sensing element 151 does not detect the light source, and thus there is no current thereon. In steady state operation, the first current switch 242 is turned on, and the second current switch 243 is turned off. When the photo-sensing component 151 has no current, the first current component 241 provides a current to charge the feedback capacitor 152, and the voltage value on the feedback terminal pin 240 rises, so that when the primary side coil 113 stores energy, its operation The upper limit of the current is increased, that is, more energy can be stored, so when it is released to the secondary side coil 131 in the second half cycle, a larger current can be provided to supply the needs of the output unit 130, and the output voltage is adjusted to recover Its rated voltage VOUT.

On the contrary, when the current value of the load current decreases, because the voltage conversion circuit 100 provides too much current to the output terminal, the excess current charges the output voltage stabilizing capacitor 133 , causing the output voltage to rise. At this time, when the divided voltage VFB of the output voltage is greater than the reference voltage of the three-terminal parallel transformer 138, the positive output terminal and the output negative terminal of the three-terminal parallel transformer 138 are conducted, that is, the light-emitting diode 137 forms a current and emits light. . The light sensing element 151 detects the light source, thus forming a current thereon, and causing the feedback capacitor 152 to discharge. The voltage value on the feedback terminal pin 240 drops, that is, when the primary side coil 113 stores energy, the upper limit of its operating current drops, that is, less energy is stored, and thus released to the secondary side coil 131 in the second half cycle A smaller current is provided to the output unit 130 to adjust the output voltage to recover its rated voltage VOUT. From the transient behavior caused by the above load current change, it can be observed that the voltage conversion controller 200 can make corresponding operations by using the negative feedback control mechanism established with the application circuit to adjust the output voltage so that the output voltage maintain a rated voltage VOUT. Or the voltage conversion circuit 100 is in a steady state operation state at this time. In addition, it can be known from the above operations that the voltage on the feedback terminal pin 240 is linearly related to the magnitude of the load current, which is a characteristic of a current-mode control voltage converter. However, in other voltage converter configurations, such as a voltage-mode control voltage converter, the voltage value on the feedback terminal pin 240 is linearly related to the output voltage, which was previously The technical features that have been disclosed in the technology will not be repeated here.

However, when the voltage conversion controller 200 starts up, the steady-state operation of the output voltage has not been established, that is, the voltage conversion circuit 100 is in an unsteady-state operation state. At this time, the voltage conversion controller 200 performs a soft start operation and establishes a steady-state operation of the output voltage, so that the voltage conversion circuit 100 reaches a state of steady-state operation. The soft-start operation can effectively prevent components in the circuit from being operated in extreme conditions at the beginning of the circuit and reduce their service life, and can reduce the surge generated in the power supply unit 110 when the circuit is started. The longer the soft-start operation is allowed, the better the protection effect it can achieve. However, the circuit start-up time must consider the application system specification and usually has a maximum limit, thus forming a design trade-off. The soft-start operation of the voltage conversion controller 200 will be described in conjunction with the waveform diagram of FIG. 3 .

FIG. 3 is a schematic diagram of the voltage waveforms of each main terminal when the voltage conversion controller 200 performs a soft-start operation. Wherein 310 is the output voltage waveform, 320 is the output waveform of the oscillation controller 255, 330 is the voltage waveform on the feedback terminal pin 240, 331 is a first comparison voltage value of the oscillation controller 255, 332 is the oscillation controller 255 A second comparison voltage value, 340 is the output waveform of the current-limiting control stage 215, 341 is the equivalent current-limiting voltage value of the current-limiting control stage 215 when the voltage conversion circuit 100 is in steady-state operation, and 350 is the current-sensing voltage pin The voltage waveform at 220 , that is, the voltage waveform of VCS, 360 is the area of the partially enlarged waveforms at 340 and 350 shown in FIG. 4 .

As shown in FIG. 3 , since the output of the oscillation controller 255 controls one of the first current switch 242 and the second current switch 243 to be turned on, when the voltage conversion controller 200 starts to start, the feedback terminal pin 240 The voltage on is smaller than the first comparison voltage value 331, so the first current switch 242 is turned on, and the first current component 241 provides a current to flow into the terminal of the feedback terminal pin 240, and because the output voltage has not been established, it reacts to the light sensing The component 151 has no current, so the current provided by the first current component 241 charges the feedback capacitor 152, so the voltage on the feedback terminal pin 240 continues to rise until it is greater than the first comparison voltage value 331, at this time the oscillation controller The output of 255 changes, the first current switch 242 is switched off, and the second current switch 243 is switched on. At this time, the second current component 244 provides a current to flow out of the terminal of the feedback terminal pin 240, causing the feedback capacitor 152 to discharge, so the voltage on the feedback terminal pin 240 begins to drop continuously until it is less than the second comparison voltage value 332, at this time The output of the oscillation controller 255 changes, the first current switch 242 is turned on, and the second current switch 243 is turned off, and the voltage on the feedback terminal pin 240 starts to rise continuously, finally forming a periodic waveform part as shown in 330 share. The output of the oscillation controller 255 also forms a periodic waveform portion as shown at 320 . In addition, the size of the period can be directly determined by the capacitance of the feedback capacitor 152 .

To further illustrate, the combination of the oscillation controller 255 , the first current component 241 , the first current switch 242 , the second current switch 243 , and the second current component 244 forms a charging and discharging circuit 280 , as shown in FIG. 2 . The charging and discharging circuit 280 periodically charges and discharges the feedback capacitor 152 in the second mode to form the aforementioned periodic waveform. The oscillation controller 255 changes the output level of the oscillation controller 255 when the voltage of the feedback capacitor 152 rises to the first comparison voltage value 331 and falls to the second comparison voltage value 332 respectively.

As shown in FIG. 3 , under soft-start operation, the output of the current-limiting control stage 215 is not the voltage value shown at 341 at the beginning, but sets the current-limiting value of the power switch 171 in a step-by-step manner. Size, in order to achieve the purpose of soft start protection circuit components and reduce circuit surge. FIG. 4 shows a region 360 of partially enlarged waveforms of 340 and 350 in FIG. 3 . When the internal oscillator 213 sends out pulses to turn on the power switch 171, the voltage waveform 350 on the current-sensing voltage pin 220 at this time, that is, VCS, is a linearly rising waveform until it is greater than the value set by the current-limiting control stage 215 , that is, 340 in the figure, so that the PWM comparator 214 outputs "1", and the power switch 171 is turned off until the internal oscillator 213 sends out a pulse next time. Therefore, a periodic signal of VCS as shown in the figure is formed.

Please go back to Figure 3. As shown in FIG. 3, the counter 251 in the voltage conversion controller 200 can use the periodic waveform formed by the output of the aforementioned oscillation controller 255 to count and output the result to the soft-start control circuit 252. The soft-start control circuit 252 That is, the output of the current-limiting control stage 215 is gradually increased according to the counting result, so as to achieve the soft-start operation. It is worth noting that the period of the output of the oscillation controller 255 will determine the duration of the soft-start operation. Therefore, in circuit applications, the user can directly change the capacitance value of the feedback capacitor 152 outside the voltage conversion controller 200. Design the time of soft start operation, so that the voltage conversion controller 200 of the same design can be used in various applications, thereby reducing the number of versions of integrated circuit components derived from various applications, and simplifying the manufacturer's production and inventory , Management issues.

In addition, when the voltage conversion circuit 100 is operating in a steady state, if the load current increases and is greater than the output current that the voltage conversion circuit 100 can supply, the voltage conversion controller 200 will be triggered to perform an unsteady operation for output overcurrent protection. . The purpose of the output over-current protection is to prevent the circuit components from being damaged due to the over-current operating condition, or even burn, which may lead to safety hazards in use. The output overcurrent protection operation of the voltage conversion controller 200 will be described with the waveform diagram of FIG. 5 .

FIG. 5 is a schematic diagram of the voltage waveforms of each main terminal when the voltage conversion controller 200 performs the output overcurrent protection operation. Wherein 510 is the output waveform of the overload protection control circuit 253, 520 is the output waveform of the oscillation controller 255, 530 is the voltage waveform on the feedback pin 240, 531 is a first comparison voltage value of the oscillation controller 255, 532 is a second comparison voltage value of the oscillation controller 255 , 540 is the output waveform of the current-limiting control stage 215 , and 550 is the voltage waveform of the current-sensing voltage pin 220 , that is, the voltage waveform of VCS.

As shown in FIG. 5 , the voltage conversion circuit 100 is initially in a steady-state operation state. At a time point t1, the load current at the output terminal increases and is greater than the output current that the voltage conversion circuit 100 can supply. At this time, due to the insufficient supply current capability of the voltage conversion circuit 100, the output voltage is continuously lower than the rated output voltage VOUT . In response to the light sensing element 151 , the light source is not detected, so there is no current thereon. Therefore, the current of the first current component 241 continues to charge the feedback capacitor 152, and the voltage on the feedback terminal pin 240 continues to rise until it is greater than the first comparison voltage value 531. At this time, the output of the oscillation controller 255 changes, and the first The current switch 242 is turned on, and the second current switch 243 is turned on.

At this time, the second current component 244 provides a current to flow out of the terminal of the feedback terminal pin 240, causing the feedback capacitor 152 to discharge, so the voltage on the feedback terminal pin 240 begins to drop continuously until it is less than the second comparison voltage value 532, at this time The output of the oscillation controller 255 changes, and the first current switch 242 is turned on, and the second current switch 243 is turned off, and the voltage on the feedback terminal pin 240 starts to rise continuously, finally forming a periodic waveform part as shown in 530 . The output of the oscillation controller 255 also forms a periodic waveform portion as shown at 520 . In addition, the size of the period can be directly determined by the capacitance of the feedback capacitor 152 .

As shown in Figure 5, the counter 251 in the voltage conversion controller 200 can use the periodic waveform formed by the output of the aforementioned oscillation controller 255 to count, and send a signal to the overload protection control circuit 253 when reaching a preset value, An action of output overcurrent protection is performed, such as notifying the shutdown logic circuit 254 to keep turning off the power switch 171 without outputting current. As shown at time t2 in FIG. 5 , at this time, the output waveform 510 of the overload protection control circuit 253 sends out a pulse wave, the power switch 171 is turned off, and the voltage waveform 550 on the current-sensing voltage pin 220 , that is, the voltage of VCS, continues to be 0. .

It can be seen from the operation of this embodiment that when the voltage conversion circuit 100 is in a steady state operation state, the feedback signal, that is, the voltage signal on the feedback terminal pin 240, is linearly related to the magnitude of the output current to provide voltage conversion control The signal required for the negative feedback control of the regulator 200 to adjust the output voltage, or it can also be explained that the voltage signal on the feedback terminal pin 240 is generated by the loop of the negative feedback control and its related components. The PWM comparator 214 receives the voltage signal on the feedback terminal pin 240 for dynamic operation. When the voltage conversion circuit 100 is in the state of non-steady operation, the count frequency signal, that is, the voltage signal on the feedback terminal pin 240, is a periodic signal, and the cycle size is determined by the external feedback capacitor. The capacitance value of 152 is determined, thus providing a relatively accurate and countable frequency signal for the non-steady-state operation, or it can also be interpreted as the voltage signal on the feedback terminal pin 240 is generated by the first Generated by the current component 241 , the first current switch 242 , the second current switch 243 , the second current component 244 , the internal voltage source 245 , the oscillation controller 255 and the feedback capacitor 152 . The oscillation controller 255 receives the voltage on the feedback terminal pin 240 to perform dynamic operation. It can be seen that the voltage signal on the feedback terminal pin 240 is generated by different circuit components of the voltage conversion controller and the application circuit under the two operating states of the voltage conversion circuit 100, and provides different functions but is different. The signals necessary for the operation of the circuit are given to two sub-circuits in the voltage conversion controller 200 , the PWM comparator 214 and the oscillator controller 255 . In contrast, the voltage on the feedback terminal pin of the voltage conversion controller in the prior art is generated by the same circuit components in any state, and can only provide meaningful signals for use when the voltage converter is operating in a steady state. Therefore, the technical features disclosed in the present invention can save the use of integrated circuit pins, thereby further saving costs; and the voltage conversion controller of the same design can be used in various applications, thus reducing the number of integrated circuit components to respond to various The number of versions derived from different applications simplifies the production, inventory, and management issues of manufacturers.

FIG. 6 shows a circuit embodiment of the swing controller 255 in the voltage conversion controller 200 . The oscillation controller 255 includes a controller input 610, a controller output 620, a first comparator 630, a second comparator 640, a first comparison voltage 650, a second comparison voltage 660, and a set Set reset latch 670. The controller input terminal 610 is coupled to the feedback terminal pin 240 , and the signal of the controller output terminal 620 is used to control the first current switch 242 and the second current switch 243 to be turned on or off. The first comparator 630 has a positive input terminal, a negative input terminal and an output terminal, wherein the positive input terminal is coupled to the controller input terminal 610 , and the negative input terminal is coupled to the first comparison voltage 650 . The second comparator 640 has a positive input terminal, a negative input terminal and an output terminal, wherein the negative input terminal is coupled to the controller input terminal 610 , and the positive input terminal is coupled to the second comparison voltage 660 . The set-reset latch 670 has a set input, a reset input, and an output, wherein the set input is coupled to the output of the first comparator 630, and the reset input The terminal is coupled to the output terminal of the second comparator 640 , and the output terminal of the set reset latch 670 is coupled to the controller output terminal 620 .

As shown in FIG. 6 , the first comparison voltage 650 is generally designed to be greater than the second comparison voltage 660 . When the voltage of the controller input terminal 610 is less than the second comparison voltage 660, the second comparator 640 outputs "1" to set the reset input terminal of the reset latch 670, so the output of the controller output terminal 620 is " 0". When the voltage at the controller input terminal 610 is greater than the first comparison voltage 650, the first comparator 630 outputs "1" to set the reset latch 670's set input terminal, so the output of the controller output terminal 620 is " 1". When the voltage at the input terminal 610 of the controller is between the first comparison voltage 650 and the second comparison voltage 660, both the first comparator 630 and the second comparator 640 output "0", and the reset latch 670 is set. The output of , that is, the output of the controller output terminal 620 remains unchanged.

Although the embodiments of the present invention are disclosed as above, they are not intended to limit the present invention. Anyone skilled in the relevant art can use the shapes, structures, and features described in the application scope of the present invention without departing from the spirit and scope of the present invention. and quantity can be slightly changed, so the scope of patent protection of the present invention must be defined by the scope of patent application attached to this specification.

Claims (12)

1. A voltage conversion controller, applied to a voltage conversion circuit, wherein the voltage conversion circuit operates a power switch to convert an input voltage into an output voltage at an output terminal, and generate a feedback signal, The feedback signal is coupled to a feedback capacitor, wherein the voltage conversion controller includes: a feedback pin, coupled to the feedback capacitor, and used to receive the feedback signal or provide a counting frequency signal; and a power switch control pin, used to control the operation of the power switch in the voltage conversion circuit; Wherein the voltage conversion controller has a first mode and a second mode; wherein in the first mode, the output terminal provides the regulated output voltage and supplies current to a current load, and the feedback The terminal pin receives the feedback signal, and the feedback signal is related to the output voltage or the current magnitude of the current load; in the second mode, the output voltage is not regulated, and the feedback terminal The pins provide the counting frequency signal with a fixed period, and the period of the counting frequency signal is determined by the capacitance value of the feedback capacitor. 2 . The voltage conversion controller according to claim 1 , wherein the second mode is a soft-start operation or a load current protection operation. 3 . 3. The voltage conversion controller according to claim 1, wherein the counting frequency signal is used as a frequency for calculating the length of time in a soft-start operation or a protection operation for a load current overload. Determining the duration of the soft start operation or the protection operation for the excessive load current. 4. The voltage conversion controller according to claim 1, wherein the voltage conversion circuit is a flyback switching power converter. 5. The voltage conversion controller according to claim 1, wherein the voltage conversion controller further comprises a charging and discharging circuit, and in the second mode, the feedback capacitor is periodically charged Discharge. 6. The voltage conversion controller according to claim 5, wherein the charging and discharging circuit further comprises: a first switch current, coupled to the feedback terminal pin, and the current direction is to flow into the feedback terminal pin; and A second switch current is coupled to the feedback terminal pin, and the current direction is to flow out of the feedback terminal pin. 7. The voltage conversion controller according to claim 6, wherein the first switch current comprises a switch component, and a current source component or a resistor component, or the second switch current comprises a switch component, and a current source component or a resistor component. 8. The voltage conversion controller according to claim 6, further comprising an oscillation controller and a counter; when the voltage converter works in the second mode, the oscillation controller utilizes the control The first switching current and the second switching current are turned on or off, and the feedback capacitor is periodically charged and discharged to form a fixed periodic counting frequency signal, which is used as the counting frequency signal of the counter. frequency source. 9. The voltage conversion controller according to claim 5, wherein the charging and discharging circuit further comprises an oscillation controller, and the oscillation controller rises to a first voltage when the voltage of the feedback capacitor is raised to a first When comparing the voltage value and dropping to a second comparison voltage value, the output level of the oscillation controller is changed. 10. The voltage conversion controller according to claim 8, wherein said oscillation controller comprises: a controller input terminal coupled to the feedback terminal pin; a controller output terminal, used to output a signal to control the conduction or termination of the first switch current and the second switch current; A first comparator having two input terminals and an output terminal, the two input terminals of which are respectively coupled to the controller input terminal and the first comparison voltage; a second comparator having two input terminals and an output terminal, the two input terminals of which are respectively coupled to the controller input terminal and the second comparison voltage; and A set-reset latch has a set input, a reset input, and an output, wherein the set input is coupled to the output of the first comparator, and the reset The set input terminal is coupled to the output terminal of the second comparator, and the output terminal of the set reset latch is coupled to the controller output terminal. 11. A voltage conversion circuit, characterized in that, the voltage conversion circuit comprises: An application circuit, and the application circuit includes an output terminal, a feedback terminal, and a feedback capacitor coupled to the feedback terminal; the output terminal has an output voltage and is coupled to a current load; and A voltage conversion controller having a feedback terminal pin coupled to the feedback terminal; wherein the voltage conversion controller has a first mode and a second mode; Wherein in the first mode, the output terminal provides the regulated output voltage and supplies current to the current load, and the feedback terminal pin provides a feedback signal, the feedback signal and the The output voltage or the current magnitude of the current load is related; in the second mode, the output voltage is not adjusted, and the feedback terminal pin receives a fixed periodic counting frequency signal, and the counting frequency signal The cycle size is determined by the capacitance of the feedback capacitor. 12. The voltage conversion circuit according to claim 11, wherein the voltage conversion circuit is a flyback switching power converter.

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