TWI514102B - Feedback detection circuit - Google Patents

Description

Feedback detection circuit

The invention relates to a feedback detection circuit, in particular to a feedback detection circuit with better transient response.

In the feedback control system, sometimes for the circuit design requirements (for example, isolation), the integrated circuit is used to feedback the detection circuit. For example, please refer to the first figure, which is a circuit diagram of a conventional optical coupling feedback circuit. An optocoupler PC in the optically coupled feedback circuit provides good isolation between the input and output. In order to control the optocoupler PC, the optical coupling feedback circuit uses a shunt regulator TL431. An output voltage Vout is supplied to a reference terminal of a voltage dividing signal input shunt regulator TL431 via a voltage divider VD. A cathode end of the shunt regulator TL431 is coupled to one end of a light-emitting diode of the optical coupler PC, and an anode terminal is grounded. The other end of the light-emitting diode in the optical coupler PC is coupled to the output voltage Vout through a resistor R to receive the power required for the illumination, and outputs a feedback detection signal FB. A compensation circuit CN is added between the cathode terminal and the reference terminal of the shunt regulator TL431 to stabilize the feedback loop. However, in some systems where the operating state is constantly switching and the speed of the transient response is high, the transient response speed of the shunt regulator TL431 often becomes a bottleneck, especially in the case of non-linear loads.

Please refer to the second figure, which is a circuit diagram of a conventional LED integrated power system (LIPS) LED dimming system. The architecture of the feedback detection circuit on the left side of the second figure is the same as that of the feedback detection circuit shown in the first figure, and only the output voltage Vout is replaced by a system voltage VCC. On the right side of the second figure, a positive terminal of a light-emitting diode module LD is coupled to a driving voltage VLED, and a negative terminal is coupled to a transistor switch M. The transistor switch M receives a pulse width modulation dimming signal DIM is turned on or off accordingly. A positive terminal of the diode D1 is coupled to a voltage dividing point of the voltage divider VD, and a negative terminal is coupled to the negative terminal of the LED module LD. When the transistor switch M is turned off, a level of the negative terminal of the LED module LD rises. At this time, the diode D1 is reversely turned off, and an operating point of the shunt regulator TL431 is determined by the voltage of the voltage dividing point of the voltage divider VD (hereinafter referred to as state one). When the transistor switch M is turned on, the level of the negative terminal of the LED module LD is lowered to turn on the diode D1, and the operating point of the shunt regulator TL431 is determined by the voltage of the negative terminal of the LED module LD. (hereinafter referred to as state two). Therefore, the feedback detection circuit switches back and forth between the above two operating states. At the moment, the LED module LD is extinguished, the load is idling, and a power supply system (not shown) that supplies the driving voltage VLED stops supplying energy to the LED module LD. In the second state, the LED module LD is lit and the load is full. The power supply system needs to immediately supply enough energy to maintain the stable brightness of the LED module LD. However, due to the limitation of the transient response speed of the shunt regulator TL431, the power system cannot immediately switch from no-load to full load, thus causing insufficient energy supply of the negative power system when the state is switched to state two, so that the light-emitting diode The body module LD flashes.

In view of the application limitation of the transient response speed of the feedback detection circuit in the prior art, the present invention utilizes a signal limiting circuit to limit one of the feedback signals generated by the feedback detection circuit, so that When the state is switched, the adjustment range of an arithmetic conversion circuit of the feedback detection circuit can be reduced or even not adjusted, thereby achieving the advantage of improving the transient response speed.

To achieve the above objective, the present invention provides a feedback detection circuit, which is adapted to provide a feedback detection signal, so that a conversion circuit generates a driving power source to drive a load according to the feedback detection signal. The feedback detection circuit includes an operation conversion circuit and a signal limiting circuit. The operation conversion circuit generates a feedback detection signal according to one of the points to be measured of the coupled load, wherein the operation conversion circuit has an operational amplification The operational amplifier is coupled to receive the measuring point to adjust the size of the feedback detecting signal corresponding to the level of the point to be measured. The signal limiting circuit is coupled to the operational conversion circuit for clamping the range of the feedback detection signal.

The present invention also provides another feedback detection circuit, which is adapted to provide a feedback detection signal, so that a conversion circuit generates a driving power source to drive a load according to the feedback detection signal. The feedback detection circuit includes an operation conversion circuit and a signal limiting circuit. The operation conversion circuit generates a feedback detection signal according to one of the points to be measured, wherein the operation conversion circuit has an operational amplifier, and the operational amplifier is coupled to receive the measurement point to adjust the size of the feedback detection signal corresponding to the level of the point to be measured. . The signal limiting circuit is coupled to the operational conversion circuit and determines whether to control the feedback detection signal according to a pulse signal, wherein the signal limiting circuit limits the feedback detection signal to a predetermined level when the pulse signal is in a first logic state. Bit, the pulse signal is located in a second logic state and does not limit the level of the feedback detection signal.

The above summary and the following detailed description are exemplary in order to further illustrate the scope of the claims. Other objects and advantages of the present invention will be described in the following description and drawings.

Please refer to the third figure, which is a circuit block diagram of the feedback detection circuit of the present invention. The feedback detection circuit includes an operational conversion circuit 110 and a signal limiting circuit 120. The operation conversion circuit 110 generates a feedback detection signal Sd according to one of the points to be measured coupled to a load (not shown). The signal limiting circuit 120 is coupled to the operational conversion circuit 110 for clamping the range of the feedback detection signal Sd. For example, the maximum level of the feedback detection signal Sd is lowered or/and the minimum level is increased, so that the feedback detection signal Sd is fed back when the feedback detection circuit performs state switching according to the level MP of the point to be measured. The detection signal Sd does not need to be adjusted by the maximum value or the minimum value, so the adjustment range of the operation conversion circuit is reduced to achieve the advantage of speeding up the reaction speed. Alternatively, the dimming signal can be modulated according to a pulse width, and when the representative is OFF (OFF), the feedback detection signal Sd is directly limited to the detection. One of the test signals Sd is located at a predetermined level. Therefore, the feedback detection circuit of the present invention can be adapted to provide a feedback detection signal Sd to a conversion circuit (not shown), so that the conversion circuit generates a driving power source to drive the load according to the feedback detection signal Sd, and satisfies A system that constantly switches between operating conditions and requires a higher speed of transient response.

Please refer to the fourth figure, which is a circuit diagram of a feedback detection circuit applied to a light-emitting diode pulse dimming system according to a first preferred embodiment of the present invention. In order to better understand the advantages of the present invention, it is exemplified based on the light-emitting diode pulse dimming system shown in FIG. Of course, the feedback detection circuit of the present invention can also be applied to different application environments such as linear loads without being limited by the description of the embodiments. In this embodiment, the feedback detection circuit includes an operational conversion circuit 210 and a signal limiting circuit 220. The operation conversion circuit 210 is a shunt voltage regulator for generating a feedback detection signal Sd according to one of the points to be measured. The feedback detection signal Sd is transmitted to a conversion controller 200 to control a voltage conversion circuit 250 to generate a driving voltage VLED. The signal limiting circuit 220 is coupled between the operational conversion circuit 210 and the resistor R to limit the maximum value of the feedback detection signal Sd to limit the range of the feedback detection signal Sd. In this embodiment, the signal limiting circuit 220 includes a Zener diode. When the transistor switch M is turned off, the level of the negative terminal of the LED module LD rises. At this time, the reverse turn-off of the diode D1 causes the level MP of the point to be measured to rise, and the operation conversion circuit 210 reduces the current flowing into the cathode end to cause a level of the feedback detection signal Sd to rise until the signal limiting circuit 220 crosses the signal. The voltage is lower than the breakdown voltage of the Zener diode. Compared with the threshold of the cathode terminal of the shunt regulator TL431 in the second figure, the level of the feedback detection signal Sd of the present embodiment is reduced by the signal limiting circuit 220. The rise in the level of the feedback detection signal Sd causes the conversion controller 200 to decrease an output power of the voltage conversion circuit 250. When the transistor switch M is turned on, the level of the negative terminal of the LED module LD is lowered. At this time, the diode D1 is turned on so that the level MP of the point to be measured is also decreased by at least one lower level than the system voltage VCC minus one of the breakdown voltages of the Zener diode. Therefore, the operation turns The amplitude of the adjustment required for the circuit 210 is reduced to achieve the effect of increasing the transient response speed.

Referring to FIG. 5, it is a circuit diagram of a feedback detection circuit according to a second preferred embodiment of the present invention. The feedback detection circuit includes an operational conversion circuit 310, a signal limiting circuit 320, and a state control circuit 330. In contrast to the embodiment shown in the fourth figure, in the present embodiment, the transistor switch M is replaced by a controlled current source I. The operation conversion circuit 310 is coupled to an optical coupler PC to generate a feedback detection signal Sd for isolation. The signal limiting circuit 320 includes a transistor M2 and a resistor R2 connected in series, one end of which is coupled to the operational conversion circuit 310 via a resistor R, and the other end is grounded. The state control circuit 330 includes a transistor M1 and a resistor R1 connected in series, one end of which is coupled to the operation conversion circuit 310 and the other end of which is grounded. In this embodiment, the transistor may be a gold oxide half field effect transistor, a bipolar transistor or other component having a switching function.

The transistor M2 of the pulse width modulation signal PWM control signal limiting circuit 320 and the transistor M1 of the state control circuit 330 are turned on and off, and the controlled current source I is controlled by an inverter 340. When the pulse width modulation signal PWM is at a low level (hereinafter referred to as a second logic state), the controlled current source I provides a predetermined current to cause a light emitting diode module LD to emit light, and at the same time, the transistors M1 and M2 are both The cutoff causes the signal limiting circuit 320 and the state control circuit 330 to have no effect. At this time, a voltage divider VD supplies a current I1 through a diode D1. When the pulse width modulation signal PWM is at a high level (hereinafter referred to as a first logic state), the controlled current source I stops supplying current, so that the light emitting diode module LD is extinguished. At this time, the transistor M2 is turned on, so that the current flowing through the optocoupler PC is increased to lower the level of the generated feedback detection signal Sd, so that a conversion circuit (not shown) for receiving the feedback detection signal Sd is received. Reduce the power output to the LED module LD. At the same time, the transistor M1 is turned on, so that the voltage divider VD provides a current I2 flowing through the state control circuit 330. The current I2 can be set to be slightly larger or slightly smaller than the current I1, so that the state of the operation conversion circuit 310 is close to the state of the pulse width modulation signal PWM in the second logic state, and preferably the current I2 is equal to the current I1. By The state control circuit 330, when the pulse width modulation signal PWM is in the first logic state, provides a virtual level to replace the level of a point to be measured when the state control circuit 330 is not present, so that at least the operation conversion circuit 310 The state of the part of the internal circuit is close to or equal to each other when the pulse width modulation signal PWM is in the first logic state and the second logic state, thereby achieving the advantage of speeding up the reaction speed.

6 is a circuit diagram of a feedback detection circuit according to a third preferred embodiment of the present invention. In the present embodiment, an operational conversion circuit 410 includes an operational amplifier in place of the shunt regulator of the embodiment shown in FIG. 5 (generally, there is also an operational amplifier inside the shunt regulator). Since the function of the compensation circuit CN is to compensate for the feedback control, it is not necessary, and in some application environments where isolation is not required, the optical coupler is not required, and is omitted in this embodiment. The feedback detection circuit includes an arithmetic conversion circuit 410, a signal limiting circuit 420, and a state control circuit 430. The signal limiting circuit 420 includes a transistor M4 and a resistor R4 connected in series. The state control circuit 430 includes a voltage divider VD and a transistor M3.

When the pulse width modulation signal PWM is in the second logic state, a controlled current source I provides a predetermined current to cause a light emitting diode module LD to emit light, and at the same time, the transistors M3 and M4 are all turned off so that the signal limiting circuit 420 and state control circuit 430 have no effect. One of the operational amplifiers of the operational conversion circuit 410 is coupled to one of the negative terminals of the LED module LD through a diode D1, and a non-inverting terminal receives a reference voltage Vr for outputting a reference. The detection signal Sd is given. At this time, the signal limiting circuit 420 does not limit the level of the feedback detecting signal Sd because the transistor M4 is turned off. When the pulse width modulation signal PWM is in the first logic state, the controlled current source I stops supplying current, so that the light emitting diode module LD extinguishes the level of the negative terminal of the light emitting diode module LD. At this time, the transistor M3 is turned on, so that the voltage divider VD in the state control circuit 430 acts to limit the level of the inverting terminal of the operational amplifier in the operational conversion circuit 410 to a level, so that the diode D1 is reversed. The state of the operational amplifier in the arithmetic conversion circuit 410 is maintained and simultaneously maintained. At the same time, the transistor M4 is also turned on, and the voltage is divided by the resistors R4 and R5. The function also limits the level of the feedback detection signal Sd to a predetermined level, so that the conversion circuit (not shown) reduces the power supplied to the LED module LD. With the above circuit architecture, the state of the operation conversion circuit 410 is closer to the prior art than when the pulse width modulation signal PWM is located in the first logic state and the second logic state, thereby achieving the advantage of speeding up the reaction speed.

Referring to FIG. 7, a circuit diagram of a feedback detection circuit according to a fourth preferred embodiment of the present invention. An operational conversion circuit 510 of the present embodiment includes an operational amplifier, and a signal limiting circuit 520 includes a transistor coupled to the operational conversion circuit 510 via an optical coupler PC. A light-emitting diode module LD is driven to emit light by a driving voltage VLED generated by a conversion circuit (not shown). A controlled current source I provides or stops supplying a current through the LED module LD according to a pulse width modulation dimming signal DIM. A voltage divider VD is coupled to a system voltage VCC through a resistor R6 for providing a voltage division signal to one of the operational amplifiers of the operational conversion circuit 510, and the opposite end of the operational amplifier receives a reference. Voltage Vr. A positive terminal of the diode D1 is coupled to the non-inverting terminal of the operational amplifier, and a negative terminal is coupled to a negative terminal of the LED module LD. The operation conversion circuit 510 is coupled to the optical coupler PC to generate a feedback detection signal Sd.

When the pulse width modulation dimming signal DIM is at a high level, the controlled current source I provides a predetermined current to cause the light emitting diode module LD to emit light. At this time, the potential of the negative terminal of the LED module LD is low, and the diode D1 is turned on to pull down the potential of the voltage dividing point of the voltage divider VD. At this time, the level of an output signal of the operational amplifier of the operational conversion circuit 510 is lowered, and the transistor in the signal limiting circuit 520 is turned on. The optocoupler PC generates the feedback detection signal Sd according to the level of the output signal of the operational amplifier. When the pulse width modulation dimming signal DIM is at a low level, the controlled current source I stops supplying a predetermined current to extinguish the LED module LD. At this time, the negative terminal potential of the LED module LD is high, and the diode D1 is reversely turned off. At this time, the level of the non-inverted terminal of the operational amplifier of the operational conversion circuit 510 is determined by the resistance of the resistor R6 and the voltage divider VD but higher than the level when the light-emitting diode module LD emits light, so that the operational amplifier The output signal level has risen. Signal limit One of the control terminals of the transistor 520 is coupled to the resistor R6, so the level of the control terminal is also determined by the resistor R6 and the resistor in the voltage divider VD, so that the connection point between the signal limiting circuit 520 and the optical coupler PC is The potential rises below a predetermined voltage difference between the resistor R6 and the voltage divider VD connection point. That is, when the output signal of the operation conversion circuit 510 is higher than a predetermined clamp level, the transistor in the signal limiting circuit 520 is turned off at this time to limit the maximum value of the potential of the connection point between the signal limiting circuit 520 and the photocoupler PC. , thereby limiting the range of the feedback detection signal Sd.

As described above, the present invention fully complies with the three requirements of the patent: novelty, advancement, and industrial applicability. The invention has been described above in terms of the preferred embodiments, and it should be understood by those skilled in the art that the present invention is not intended to limit the scope of the invention. It should be noted that variations and permutations equivalent to those of the embodiments are intended to be included within the scope of the present invention. Therefore, the scope of the invention is defined by the scope of the following claims.

Prior art:

PC‧‧‧Optocoupler

TL431‧‧‧Shunt Regulator

Vout‧‧‧ output voltage

VD‧‧‧ voltage divider

R‧‧‧resistance

FB‧‧‧ feedback detection signal

CN‧‧‧compensation circuit

VCC‧‧‧ system voltage

LD‧‧‧Light Diode Module

VLED‧‧‧ drive voltage

M‧‧‧Crystal Switch

DIM‧‧‧ pulse width modulation dimming signal

D1‧‧‧ diode

this invention:

110, 210, 310, 410, 510‧‧‧ arithmetic conversion circuit

120, 220, 320, 420, 520‧‧‧ signal limiting circuit

MP‧‧‧Points to be tested

Sd‧‧‧Reward detection signal

200‧‧‧Transition controller

250‧‧‧Voltage conversion circuit

VLED‧‧‧ drive voltage

R, R1, R2, R4, R5, R6‧‧‧ resistance

D1‧‧‧ diode

I‧‧‧controlled current source

PC‧‧‧Optocoupler

M1, M2, M3, M4‧‧‧ transistors

PWM‧‧‧ pulse width modulation signal

I1, I2‧‧‧ current

Vr‧‧‧reference voltage

DIM‧‧‧ pulse width modulation dimming signal

M‧‧‧Crystal Switch

VD‧‧‧ voltage divider

CN‧‧‧compensation circuit

VCC‧‧‧ system voltage

LD‧‧‧Light Diode Module

330, 430‧‧‧ State Control Circuit

340, 440‧‧‧ reverser

The first figure is a circuit diagram of a conventional optical coupling feedback circuit.

The second figure is a circuit diagram of a conventional LED dimming system with integrated power system architecture.

The third figure is a circuit block diagram of the feedback detection circuit of the present invention.

The fourth figure is a circuit diagram of a feedback detection circuit applied to a light-emitting diode pulse dimming system according to a first preferred embodiment of the present invention.

Figure 5 is a circuit diagram of a feedback detection circuit in accordance with a second preferred embodiment of the present invention.

Figure 6 is a circuit diagram of a feedback detection circuit in accordance with a third preferred embodiment of the present invention.

Figure 7 is a circuit diagram of a feedback detection circuit in accordance with a fourth preferred embodiment of the present invention.

110‧‧‧Operation conversion circuit

120‧‧‧Signal limiting circuit

MP‧‧‧Points to be tested

Sd‧‧‧Reward detection signal

Claims (9)

A feedback detection circuit is provided for providing a feedback detection signal, so that a conversion circuit generates a driving power source to drive a load according to the feedback detection signal, and the feedback detection circuit comprises: an operation conversion circuit, The feedback detection signal is generated according to one of the points to be measured coupled to the load, wherein the operation conversion circuit has an operational amplifier coupled to the point to be measured to correspond to the point to be measured. The bit adjusts the size of the feedback detection signal; and a signal limiting circuit coupled to the operational conversion circuit for clamping the range of the feedback detection signal. The feedback detection circuit of claim 1, wherein the operation conversion circuit is a shunt regulator. The feedback detection circuit of claim 1 or 2, wherein the signal limiting circuit comprises a Zener diode. The feedback detection circuit of claim 1 or 2, wherein the signal limiting circuit comprises a transistor switch, wherein the output signal of the operational conversion circuit is higher than a predetermined clamp level. The crystal switch is turned off. A feedback detection circuit is provided for providing a feedback detection signal, so that a conversion circuit generates a driving power source to drive a load according to the feedback detection signal, and the feedback detection circuit comprises: an operation conversion circuit, Generating a feedback detection signal according to one of the points to be measured, wherein the operation conversion circuit has an operational amplifier coupled to the point to be measured to adjust the feedback to the level of the point to be measured Detecting the size of the signal; and a signal limiting circuit coupled to the operational conversion circuit and determining whether to control the feedback detection signal according to a pulse signal, wherein the signal limiting circuit is in the pulse When the ping signal is in a first logic state, one of the feedback detection signals is limited to a predetermined level, and the pulse signal is located in a second logic state, and the level of the feedback detection signal is not limited. The feedback detection circuit of claim 5, further comprising a state control circuit coupled to the operation conversion circuit, the state control circuit providing a virtual state when the pulse signal is in the first logic state The level is substituted to replace the level of the point to be tested. The feedback detection circuit of claim 5, wherein the signal limiting circuit comprises a transistor switch, and the transistor switch switches according to the pulse signal to enable the feedback detection signal. The pulse signal is located at the predetermined level when the pulse signal is in the first logic state. The feedback detection circuit of claim 5 or 6, wherein the operation conversion circuit is a shunt regulator. The feedback detection circuit of claim 6, wherein the state control circuit comprises a transistor switch, wherein the transistor switch is switched according to the pulse signal, so that the state control circuit is located at the first pulse signal This virtual level is provided in the logic state.