TWI465015B - Voltage converter circuit and voltage converter controller - Google Patents

Description

Voltage conversion circuit and voltage conversion controller

The present invention relates to a voltage conversion circuit, and more particularly to a voltage conversion circuit including a multi-function single-pin voltage conversion controller.

Please refer to US Patent No. 7,848,124. The voltage conversion controller is applied to a fly-back switching power converter. The flyback switching power converter is a type of voltage conversion circuit configured to provide a stable output voltage. When the flyback switching power conversion circuit is in steady state operation, the voltage conversion controller regulates its output voltage by negative feedback control to provide a stable and rated output voltage value and output current. Give a current load. At this time, the feedback point IN3 on the negative feedback control path has a signal, which is a signal linearly related to the magnitude of the output current, and the voltage conversion controller performs negative feedback control according to the signal on the feedback point IN3. . When the return-to-back switching power conversion circuit is in an unsteady operation, for example, when the load current is too large to perform a load current excessive protection operation, or a soft start operation of the initial startup of the circuit, the rated output voltage value at this time is not Established, and since the signal on the feedback point IN3 is related to the signal at the output end, the signal at the feedback point IN3 is finally a continuous DC voltage signal after a brief transient reaction, and for circuit operation. No functional benefits are provided.

In the current mainstream applications, the voltage conversion controller is usually implemented in an integrated circuit, and is combined with an external application circuit to form a voltage conversion circuit to achieve cost, circuit size, and flexibility in use. The integrated circuit contains external electronics The components are electrically connected to the pins, and in order to optimize the cost and volume, the number of pins of the integrated circuit can be as small as possible without affecting the elasticity of use. Therefore, in design, if the pin can be used under all circuit conditions, providing a substantial benefit function, that is, the optimal use of the pin. In the prior art of the above-mentioned example, the pin representing the feedback point does not provide a function of substantial efficiency in circuit operation when the voltage conversion controller is in an unsteady operation, which is the current general voltage conversion controller product. The general phenomenon of body circuits.

In view of the above problems, an object of the present invention is to provide a voltage conversion circuit including a voltage conversion controller, which is an integrated circuit, and the voltage conversion controller can provide a single pin having a multifunction.

The invention provides a voltage conversion circuit comprising an application circuit and a voltage conversion controller. The application circuit includes an output terminal, a feedback terminal, and a feedback capacitor coupled to one of the feedback terminals. The output has an output voltage and is coupled to a current load. The voltage conversion controller has a feedback end pin coupled to the feedback end. The voltage conversion controller has a first mode and a second mode. In the first mode, the output provides a regulated output voltage and supplies current to the current load, and the feedback pin receives a feedback signal. In the second mode, the output voltage is unregulated, and the feedback pin provides one of the fixed periodic periodic clock signals, and the period of the counting clock signal is determined by the capacitance of the feedback capacitor.

The technical features disclosed in the present invention can save the use amount of the integrated circuit pins, thereby further saving the cost; and the voltage conversion controller of the same design can be used for various applications, thereby reducing the complexity of the integrated circuit components. application The number of versions derived from the simplifies the manufacturer's production, inventory, and management issues.

In the context of the specification and subsequent patent applications, the term "coupled" is used herein to include any direct and indirect electrical connection. Therefore, if a first device is coupled to a second device, it means that the first device can be directly electrically connected to the second device or indirectly electrically connected to the second device through other devices or connection means.

FIG. 1 is a schematic circuit diagram of a voltage conversion circuit 100. The voltage conversion circuit 100 is a configuration of a flyback switching power supply 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 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 side coil 113.

The bridge full-wave rectifier 111 performs full-wave rectification of an input AC power source 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 the full-wave rectified result is regulated to generate an input voltage VIN to the input stabilizing capacitor 112.

The primary side coil 113 has a first end point and a second end point, and the first end point is coupled to the input stabilizing capacitor 112. The power supply unit 110 is mainly used to provide an input voltage VIN to the primary side coil 113.

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

The secondary side coil 131 has a first end point and a second end point, and has a mutual inductance relationship with the primary side coil 113 to form a transformer element.

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

The other end of the output voltage stabilizing capacitor 133 is coupled to the second end of the secondary side coil 131 and forms a negative terminal VON of the output end. 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 of the second feedback resistors 135. The other end of the second feedback resistor 135 is coupled to the negative terminal VON of the output terminal. The junction of the first feedback resistor 134 and the second feedback resistor 135 provides an output voltage divider VFB and is coupled to the input of the three-terminal shunt regulator 138.

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

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

As shown in FIG. 1, the three-terminal shunt regulator 138 includes a reference voltage value. When the voltage at the input terminal is greater than the reference voltage value, the output positive terminal and the output negative terminal of the three-terminal shunt regulator 138 are one. The state of conduction. Conversely, when the voltage at its input is small At the reference voltage value, a non-conducting state is between the positive output terminal and the negative output terminal of the three-terminal shunt regulator 138. 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 current magnitude is limited by the current limiting resistor 136. The light-emitting diode 137 forms a light source for illumination; 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 turned on, and the light-emitting diode 137 has no current, that is, the light-emitting diode The polar body 137 does not emit light.

As shown in FIG. 1, the power switch unit 170 includes a power switch 171 and a current-sense resistor 172. The output of the power switch 171 is connected in series with the sense resistor 172 and coupled between the second end of the primary side coil 113 and the ground. When the power switch 171 is turned on, the input stabilizing capacitor 112, the primary side coil 113, the power switch 171, and the sense resistor 172 form a current loop. Since the primary side coil 113 is an inductive component, the formation of the current loop stores energy on the primary side coil 113. In addition, the current sensing 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 is transmitted through the transformer element formed by the secondary side coil 131, and is discharged to the secondary side coil 131 to form a current thereon, and is stabilized in the voltage conversion circuit 100. In the state operation, a rated output voltage VOUT is established between the positive terminal and the negative terminal of the output terminal, and a current load is supplied between the positive terminal and the negative terminal of the output terminal (not shown). .

As shown in FIG. 1, the feedback circuit unit 150 includes a light sensing element 151 and a feedback capacitor 152. The light sensing element 151 and the light emitting diode 137 form a configuration of an optical coupler. When the light emitting diode 137 forms a light source, the light sensing element The device 151 detects the light source to form a current thereon, and the magnitude of the current is proportional to the intensity of the light source. Therefore, it can be seen that the transformer and the optical coupler can completely electrically isolate one side of the input AC power source from one side of the output end.

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

FIG. 2 is a 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 driver stage 211, a pulse width modulation latch 212, an internal oscillator 213, a pulse width modulation comparison The device 214, a current limiting control stage 215, and a gain stage 221.

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

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

The first current element 241 and the first current switch 242 are connected in series to form a switch A current component, wherein the first current component 241 can be a resistive component or a current source component.

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

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

The input of the oscillating controller 255 is coupled to the feedback terminal pin 240, and generates a periodic clock signal at its output terminal during the non-steady operation of the voltage conversion circuit 100, thereby controlling the first current switch 242 and the second current. The switch 243 is turned on and off.

The output 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 during the non-steady state operation of the voltage conversion circuit 100.

The overload protection control circuit 253 controls the shutdown logic circuit 254 according to the setting to determine whether to temporarily turn off the voltage conversion controller 200.

The pulse width modulation 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 terminal input of the pulse width modulation comparator 214. Gain stage 221 is to linearly amplify its input signal and output it. The current limiting control stage 215 provides a voltage value of the equivalent current limit at its output and is coupled to the second negative terminal input of the pulse width modulation comparator 214.

The pulse width modulation latch 212 has a set input, a reset input, and An output. The reset input is coupled to the output of the pulse width modulation comparator 214. The internal oscillator 213 provides a pulse width modulation operation clock and is coupled to the set input of the pulse width modulation latch 212.

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

The voltage conversion controller 200 cooperates with the application circuit to establish the voltage conversion circuit 100 as shown in FIG. The voltage conversion controller 200 has at least a first mode and a second mode, such as steady state operation and non-steady state operation. In the first mode, the feedback end pin 240 receives a feedback signal, and in the second mode, the feedback end pin 240 provides a count clock signal. The feedback signal and the counting clock signal have different roles in the manner of formation and operation.

During steady state operation of the voltage conversion circuit 100, the voltage conversion controller 200 feedbacks the current load between the positive terminal VOP and the negative terminal VON of the regulated output terminal and provides a regulated rated output voltage VOUT to the output voltage. The so-called regulator means that when the external application circuit and the current load parameters are changed within the specification range, the voltage conversion controller 200 can react with the negative feedback control mechanism established by the external application circuit to Keep the output voltage at a nominal VOUT.

When the voltage conversion circuit 100 is in an unsteady operation, the voltage conversion controller 200 cooperates with the application circuit to perform necessary reactions to protect the voltage conversion controller 200, the components in the application circuit, and the current load, thereby protecting the application circuit from the application circuit. Because of electricity In the event of a voltage or overcurrent, the component is damaged or otherwise malfunctions. Common unsteady operation reactions include soft start, input voltage under-lock, output over-voltage protection, output over-current protection, and more. Embodiments of the present invention will be described with respect to the technical features of the steady state operation of voltage conversion circuit 100, as well as the non-steady state operation of soft start and output over current protection.

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

At the beginning of one of the cycles, the internal oscillator 213 of the voltage conversion controller 200 outputs a pulse wave to trigger the set input terminal of the pulse width modulation latch 212 to generate a signal "1" for triggering the pulse width modulation latch 212. At the output, the power switch driver 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 on the primary side coil 113. At this time, the transformer does not supply current to the output terminal, so the current load required at the output terminal is derived from the output voltage stabilizing capacitor 133, so the output voltage linearly decreases. Since the current on the primary side coil 113, that is, the current on the power switch 171 continues to rise, the voltage signal VCS on the sense voltage pin 220 also continues to rise until the VCS is greater than the voltage value on the feedback terminal pin 240. The clock width modulation comparator 214 outputs a signal "1" to the reset input of the pulse width modulation latch 212 to generate a signal "0" at the output of the pulse width modulation latch 212, the power switch driver stage 211 thus turns off the power switch 171. The stored energy on the primary side coil 113 is transmitted through the transformer element formed by the secondary side coil 131, and is discharged to the secondary side coil 131 to form a current thereon. Current is supplied to the load current and the output voltage stabilizing capacitor 133 is charged. At this time, the output voltage rises linearly until the internal oscillator 213 generates the next pulse wave, and the power switch 171 is turned on. The voltage conversion circuit 100 thus performs periodic operations.

When the current value of the load current increases, since the voltage conversion circuit 100 temporarily cannot supply sufficient current to the load current, the output stabilizing capacitor 133 supplies the required extra charge, thereby causing the output voltage to drop. When the divided voltage VFB of the output voltage is lower than the reference voltage of the three-terminal shunt regulator 138, the output positive terminal and the output negative terminal of the three-terminal parallel voltage regulator 138 are not turned on, that is, the output of the light-emitting diode 137. No current and no light. The light sensing element 151 does not detect the light source and thus has 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 light sensing element 151 does not have a current, the first current element 241 provides a current to charge the feedback capacitor 152, and the voltage value on the feedback terminal pin 240 rises, causing the primary side coil 113 to operate when the energy is stored. The upper limit of the current is increased, that is, more energy can be stored, so that a larger current can be supplied to the secondary side coil 131 when the second half cycle is released to provide the output unit 130, and the output voltage is adjusted to recover Its rated voltage is VOUT.

On the contrary, when the current value of the load current decreases, since the voltage conversion circuit 100 supplies too much current to the output terminal, the excess current charges the output voltage stabilizing capacitor 133, causing the output voltage to rise. When the divided voltage VFB of the output voltage is greater than the reference voltage of the three-terminal parallel voltage regulator 138, the output positive terminal of the three-terminal parallel voltage regulator 138 is turned on, that is, the light-emitting diode 137 forms a current. Glowing. The light sensing element 151 detects the light source, thereby forming a current thereon and causing the feedback capacitor 152 to discharge. The voltage value on the feedback terminal pin 240 decreases, that is, when the primary side coil 113 enters When the energy is stored, the upper limit of the operating current is decreased, that is, less energy is stored, so that a smaller current is supplied to the output unit 130 when the second half of the coil is released to the secondary side coil 131, thereby adjusting the output voltage. To restore its rated voltage VOUT. From the transient behavior caused by the above change of the load current, it can be observed that the voltage conversion controller 200 can perform corresponding operations by using the negative feedback control mechanism established by the voltage conversion controller and the application circuit, and adjust the output voltage to make the output The voltage is maintained at a nominal voltage VOUT. Or the voltage conversion circuit 100 is in a state of steady state operation at this time. In addition, as can be seen from the above operation, the voltage value on the feedback terminal pin 240 is linearly related to the magnitude of the current of the load current, which is a characteristic of a current-mode control voltage conversion controller. However, in other voltage conversion controller configurations, such as a voltage-mode control voltage conversion controller, the voltage value on the feedback terminal pin 240 is linearly related to the output voltage magnitude. For the technical features that have been disclosed in the prior art, no further details are provided herein.

When the voltage conversion controller 200 is just started, the steady state operation of the output voltage has not been established, that is, the voltage conversion circuit 100 is in an unsteady state. At this time, the voltage conversion controller 200 performs a soft start operation and establishes a steady state operation of the output voltage to bring the voltage conversion circuit 100 to a state of steady state operation. The soft-start operation can effectively prevent the components in the circuit from operating at a limit condition at the beginning of the circuit, thereby reducing the service life of the components, and reducing the surge generated by the power supply unit 110 when the circuit is started. The longer the soft-start operation allows, the better the protection it can achieve. However, the circuit startup time must take into account the system specifications on the application and usually has a maximum limit, thus forming a design trade-off. Voltage turn The soft start operation of the controller 200 will be described in conjunction with the waveform diagram of FIG.

FIG. 3 is a schematic diagram showing voltage waveforms of respective main terminals when the voltage conversion controller 200 performs a soft start operation. 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 the first comparison voltage value of the oscillation controller 255, and 332 is the oscillation controller 255. a second comparison voltage value, 340 is the output waveform of the current limit control stage 215, 341 is the voltage value of the current limit control current of the current limit control stage 215 under the steady state operation of the voltage conversion circuit 100, and 350 is the current sense voltage pin. The voltage waveform on 220, that is, the voltage waveform of VCS, 360 is the area of the 340 and 350 partially amplified waveforms shown in FIG.

As shown in FIG. 3, since the output of the oscillation controller 255 controls to turn on one of the first current switch 242 and the second current switch 243, when the voltage conversion controller 200 starts to be activated, the feedback end pin is The voltage on 240 is less than the first comparison voltage value 331, so the first current switch 242 is turned on, the first current element 241 provides a current flowing into the end of the feedback end pin 240, and since the output voltage is not established, the reaction to the light The sensing element 151 has no current, so the current supplied by the first current element 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. The output of the controller 255 changes, the first current switch 242 is turned off, and the second current switch 243 is turned on. At this time, the second current component 244 provides a current flowing out of the end of the feedback terminal pin 240, causing the feedback capacitor 152 to discharge, so that the voltage on the feedback terminal pin 240 begins to continuously decrease until it is less than the second comparison voltage value 332. When the output of the oscillation controller 255 changes, the first current switch 242 is turned on, and the second current switch The 243 switch is turned off, and the voltage on the feedback terminal pin 240 begins to rise continuously, eventually forming a periodic waveform portion as shown at 330. The output of the oscillating controller 255 also forms a periodic waveform portion as indicated at 320. In addition, the size of the period can be directly determined by the capacitance value of the feedback capacitor 152.

Further, the combination of the oscillation controller 255, the first current element 241, the first current switch 242, the second current switch 243, and the second current element 244 forms a charge and discharge circuit 280, as shown in FIG. When the charge and discharge circuit 280 is in the second mode, the feedback capacitor 152 is periodically charged and discharged 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 drops to the second comparison voltage value 332, respectively.

As shown in FIG. 3, in the soft start operation, the output of the current limiting control stage 215 is not the voltage value as shown in 341 at the beginning, but is set in a stepwise increment manner to set the current limit of the power switch 171. Size to achieve soft start protection circuit components and reduce circuit spurs. Figure 4 shows the area 360 of the partially magnified waveform of 340 and 350 in Figure 3. When the internal oscillator 213 emits a pulse wave to open the power switch 171, the voltage waveform 350 on the sense voltage pin 220, that is, the VCS, is a waveform that rises in a straight line until it is greater than the value set by the current limit control stage 215. That is, 340 in the figure causes the pulse width modulation comparator 214 to output "1", and the power switch 171 is turned off until the next internal oscillator 213 emits a pulse wave. Therefore, a periodic signal of the VCS in the figure is formed.

Please return to Figure 3. As shown in FIG. 3, the counter 251 in the voltage conversion controller 200 can utilize the periodic wave formed by the output of the aforementioned oscillation controller 255. The shape is counted and the result is output to the soft start control circuit 252. The soft start control circuit 252 gradually increases the output of the current limit control stage 215 as a result of the counting to achieve the soft start operation. It should be noted that the period of the output of the oscillation controller 255 will determine the length of the soft start operation. Therefore, in the circuit application, the user can directly change the capacitance value of the feedback capacitor 152 outside the voltage conversion controller 200. To design the time of the soft-start operation, so that the same design of the voltage conversion controller 200 can be used in a variety of different applications, thereby reducing the number of versions of the integrated circuit components in response to a variety of different applications, simplifying manufacturers' production, Inventory, management issues.

In addition, when the voltage conversion circuit 100 is in steady state operation, 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 is triggered to perform the output overcurrent protection. . The purpose of the output overcurrent protection is to prevent the circuit components from being damaged under the excessive current operating conditions, and even causing combustion to cause safety in use. The output overcurrent protection operation of voltage conversion controller 200 will be described in conjunction with the waveform diagram of FIG.

FIG. 5 is a schematic diagram showing voltage waveforms of respective main terminals when the voltage conversion controller 200 performs an output overcurrent protection operation. 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 terminal pin 240, and 531 is the first comparison voltage value of the oscillation controller 255, 532. For the 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 the VCS.

As shown in Fig. 5, the voltage conversion circuit 100 is initially in a state of steady state operation. 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, the output voltage continues to be lower than the rated output voltage due to insufficient supply current capability of the voltage conversion circuit 100. VOUT. The reaction to the light sensing element 151 is such that no light source is detected and thus no current is present thereon. The current of the first current element 241 is thus continuously charged to 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 which time the output of the oscillation controller 255 changes and the first is turned off. The current switch 242 opens the second current switch 243.

At this time, the second current component 244 provides a current flowing out of the end of the feedback terminal pin 240, causing the feedback capacitor 152 to discharge, so that the voltage on the feedback terminal pin 240 begins to continuously decrease until it is less than the second comparison voltage value 532. 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, and finally the periodic waveform portion shown as 530 is formed. . The output of the oscillating 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 value of the feedback capacitor 152.

As shown in FIG. 5, the counter 251 in the voltage conversion controller 200 can count using the periodic waveform formed by the output of the oscillation controller 255, and send a signal to the overload protection control circuit 253 when a pre-designed value is reached. The action of output overcurrent protection is performed, for example, to notify the shutdown logic circuit 254 to continuously turn off the power switch 171 without outputting current. As shown by t2 in FIG. 5, at this time, the output waveform 510 of the overload protection control circuit 253 emits a pulse wave, and the power switch 171 By the end, the voltage waveform 550 on the sense voltage pin 220, that is, the voltage of the VCS, continues to be zero.

It can be seen from the operation of this embodiment that when the voltage conversion circuit 100 is in a state of steady state operation, the feedback signal, that is, the voltage signal on the feedback terminal pin 240, is linearly related to the output current to provide a voltage conversion controller. 200 performs the signal required to adjust the negative feedback control of the output voltage, or can also be interpreted as the voltage signal on the feedback terminal pin 240 is generated by the loop controlled by the negative feedback and its related components. The pulse width modulation comparator 214 receives the voltage signal on the feedback terminal pin 240 for dynamic operation. When the voltage conversion circuit 100 is in an unsteady state, the counting clock signal, that is, the voltage signal on the feedback terminal pin 240, is a periodic signal, and the period is determined by an external feedback capacitor. The capacitance value of 152 is determined, thereby providing a clock signal with a relatively accurate frequency and available for counting, which is required for unsteady operation, or can be interpreted as a voltage signal on the feedback terminal pin 240. A current element 241, a first current switch 242, a second current switch 243, a second current element 244, an internal voltage source 245, an oscillation controller 255, and a feedback capacitor 152 are generated. The oscillating controller 255 receives the voltage on the feedback terminal pin 240 for dynamic operation. It can be seen that the voltage signal on the feedback terminal pin 240 is generated by the voltage conversion controller and the different circuit components of the application circuit in the two operating states of the voltage conversion circuit 100, and provides different functions but also circuits. The signals necessary for operation are supplied to two sub-circuits in the voltage conversion controller 200, namely the pulse width modulation comparator 214 and the oscillation controller 255. In contrast, the voltage on the feedback pin of the voltage conversion controller in the prior art is generated by the same circuit component in any state, and can only provide a meaningful signal when the voltage conversion circuit operates in steady state. For use. Therefore, the technical features disclosed in the present invention can save the use amount of the integrated circuit pins, thereby further saving cost; and the voltage conversion controller of the same design can be used for various applications, thereby reducing various integrated circuit components. Simplify the manufacturer's production, inventory, and management issues with the number of versions derived from different applications.

FIG. 6 shows an embodiment of the circuit of the sway controller 255 in the voltage conversion controller 200. The oscillating controller 255 includes a controller input terminal 610, a controller output terminal 620, a first comparator 630, a second comparator 640, a first comparison voltage 650, a second comparison voltage 660, and a setting. The latch 670 is reset. 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. 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. 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 terminal, a reset input terminal, and an output terminal, wherein the set input terminal is coupled to the output end of the first comparator 630, and the reset input terminal is coupled to the The output of the comparator 640 and the output of the reset latch 670 are coupled to the controller output 620.

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

Although the embodiments of the present invention are disclosed above, it is not intended to limit the present invention, and those skilled in the art, regardless of the spirit and scope of the present invention, the shapes, structures, and features described in the scope of the present application. And the number of modifications may be made, and the scope of patent protection of the present invention shall be determined by the scope of the patent application attached to the specification.

100‧‧‧Voltage conversion circuit

110‧‧‧Power supply unit

111‧‧‧Bridge full wave rectifier

112‧‧‧Input Stabilizing Capacitor

113‧‧‧One-side coil

130‧‧‧Output unit

131‧‧‧second side coil

132‧‧‧Output diode

133‧‧‧Output regulated capacitor

134‧‧‧First feedback resistor

135‧‧‧second feedback resistor

136‧‧‧ Current limiting resistor

137‧‧‧Lighting diode

138‧‧‧Three-terminal shunt regulator

150‧‧‧Return circuit unit

151‧‧‧Light sensing components

152‧‧‧Responsive capacitance

170‧‧‧Power switch unit

171‧‧‧Power switch

172‧‧‧Sense current resistance

200‧‧‧Voltage conversion controller

210‧‧‧Power switch control feet

211‧‧‧Power switch driver stage

212‧‧‧ Pulse width modulation latch

213‧‧‧Internal oscillator

214‧‧‧ Pulse width modulation comparator

215‧‧‧Limited current control stage

220‧‧‧Sense voltage foot

221‧‧‧ Gain level

230‧‧‧ Grounding feet

240‧‧‧Responsible end pins

241‧‧‧First current component

242‧‧‧First current switch

243‧‧‧Second current switch

244‧‧‧second current component

245‧‧‧Internal voltage source

251‧‧‧ counter

252‧‧‧Soft start control circuit

253‧‧‧Overload protection control circuit

254‧‧‧Close logic circuit

255‧‧‧Oscillation controller

280‧‧‧Charge and discharge circuit

310‧‧‧Output voltage waveform

320‧‧‧Output waveform of the oscillation controller

330‧‧‧Responding to the voltage waveform of the end pin

331‧‧‧ first comparison voltage value of the oscillation controller

332‧‧‧Second comparison voltage value of the oscillation controller

340‧‧‧ Output current waveform of current limit control stage

341‧‧‧ Voltage value of the current limit of the current limit control current in steady state operation

350‧‧‧ Voltage waveform of the sense voltage pin

360‧‧‧340 and 350 partially amplified waveform areas

510‧‧‧ Output waveform of overload protection control circuit

520‧‧‧Output waveform of the oscillation controller

530‧‧‧Responding to the voltage waveform of the terminal pin

531‧‧‧ First comparison voltage value of the oscillation controller

532‧‧‧Second comparison voltage value of the oscillation controller

Output waveform of 540‧‧‧ current limiting control stage

550‧‧ ‧ voltage waveform of the sense voltage pin

610‧‧‧controller input

620‧‧‧Controller output

630‧‧‧First comparator

640‧‧‧Second comparator

650‧‧‧First comparison voltage

660‧‧‧Second comparison voltage

670‧‧‧Set reset latch

Figure 1 is a circuit diagram of a voltage conversion circuit of the present invention.

Figure 2 is a block diagram showing the functional components of the voltage conversion controller of the present invention.

Fig. 3 is a schematic diagram showing the voltage waveforms of the main terminals when the voltage conversion controller of the present invention performs a soft start operation.

Fig. 4 is a view showing the voltage waveform of the partially enlarged region in Fig. 3.

Fig. 5 is a schematic diagram showing the voltage waveforms of the main terminals when the voltage conversion controller of the present invention performs the output overcurrent protection operation.

Fig. 6 is a circuit diagram of an oscillation controller in the voltage conversion controller of the present invention.

200‧‧‧Voltage conversion controller

210‧‧‧Power switch control feet

211‧‧‧Power switch driver stage

212‧‧‧ Pulse width modulation latch

213‧‧‧Internal oscillator

214‧‧‧ Pulse width modulation comparator

215‧‧‧Limited current control stage

220‧‧‧Sense voltage foot

221‧‧‧ Gain level

230‧‧‧ Grounding feet

240‧‧‧Responsible end pins

241‧‧‧First current component

242‧‧‧First current switch

243‧‧‧Second current switch

244‧‧‧second current component

245‧‧‧Internal voltage source

251‧‧‧ counter

252‧‧‧Soft start control circuit

253‧‧‧Overload protection control circuit

254‧‧‧Close logic circuit

255‧‧‧Oscillation controller

280‧‧‧Charge and discharge circuit

Claims (12)

A voltage conversion controller is applied to a voltage conversion circuit, wherein the voltage conversion circuit operates one of the power switches to convert an input voltage into an output voltage at an output end, and generates a feedback signal, the feedback The signal is coupled to a feedback capacitor, the voltage conversion controller includes: a feedback pin coupled to the feedback capacitor, and configured to receive the feedback signal or provide a count clock signal; and a power switch control a pin for controlling 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 provides the regulated output voltage And supplying a current to a current load, and the feedback pin receives the feedback signal, and the feedback signal is related to the output voltage or the current of the current load; in the second mode, the output voltage is not adjusted. And the feedback end pin provides a fixed periodicity of the counting clock signal, and the period of the counting clock signal is determined by the capacitance value of the feedback capacitor The voltage conversion controller of claim 1, wherein the second mode is a soft start operation or a protection operation for a load current excessive. The voltage conversion controller according to claim 1, wherein the counting clock signal is in a soft start operation or a protection operation in which a load current is too large, as a clock for calculating the length of time, to determine the soft Start operation or the load current The length of time for an excessive protection operation. The voltage conversion controller of claim 1, wherein the voltage conversion circuit is a flyback switching power converter. The voltage conversion controller according to claim 1, further comprising a charge and discharge circuit, wherein the feedback capacitor is periodically charged and discharged in the second mode. The voltage conversion controller of claim 5, wherein the charge and discharge circuit further comprises: a first switch current coupled to the feedback end pin, and the current direction is flowing into the feedback end pin; A second switch current is coupled to the feedback end pin, and the current direction is flowing out of the feedback end pin. The voltage conversion controller of claim 6, wherein the first switching current comprises a switching element, and a current source element or a resistance element, or the second switching current comprises a switching element, and a current Source element or a resistive element. The voltage conversion controller of claim 6, further comprising an oscillation controller and a counter; when the voltage conversion controller operates in the second mode, the oscillation controller utilizes the first switching current And the second switch current is turned on or off, and the feedback capacitor is periodically charged and discharged to form a fixed periodic pulse signal for use as a clock source of the counter. The voltage conversion controller according to claim 5, wherein the charging and discharging The circuit further includes an oscillating controller that changes an output level of the oscillating controller when the voltage of the feedback capacitor rises to a first comparison voltage value and decreases to a second comparison voltage value. The voltage conversion controller of claim 8, wherein the oscillation controller comprises: a controller input coupled to the feedback pin; and a controller output for outputting a signal to control The first switch current is turned on or off with the second switch current; a first comparator has two input ends and an output end, and the two input ends are respectively coupled to the controller input end and the first comparison voltage a second comparator having two inputs and an output, the two inputs being respectively coupled to the controller input and the second comparison voltage; and a set reset latch having a set input a reset input terminal and an output terminal, wherein the set input terminal is coupled to the output end of the first comparator, the reset input end is coupled to the output end of the second comparator, and the set weight is The output of the latch is coupled to the output of the controller. A voltage conversion circuit includes: 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 the a current load; and a voltage conversion controller having a feedback end pin coupled to the feedback end; Wherein the voltage conversion controller has a first mode and a second mode; wherein, in the first mode, the output provides the regulated output voltage and supplies current to the current load, and the feedback pin is provided a feedback signal, 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 adjusted, and the feedback pin receives one of the fixed periodicity counts The pulse signal, the period of the counting clock signal is determined by the capacitance value of the feedback capacitor. The voltage conversion circuit of claim 11, wherein the voltage conversion circuit is a flyback switching power converter.