TWI583088B - Controllers, power supplies and control methods - Google Patents

Description

Controller, power supply, and control method

The present invention relates to a protection circuit for a power supply.

In order to consider conversion efficiency and product volume considerations, many power supply devices are currently switching mode power supply (SMPS), which controls the conduction and deactivation of a power switch, and determines the energy storage for an inductive component. Release the energy to the power supply required for the load supply.

For example, Figure 1 is a conventional SMPS 10 having a flyback architecture. The bridge rectifier 12 rectifies AC mains AC power and provides a line voltage supply V _IN at the IN terminal, which may be as high as 100 volts to 300 volts. Through the CS terminal, the controller 18 detects the detection signal V _CS across the current detecting resistor 16, which represents the inductor current flowing through the primary winding 24 of the transformer 20 when the power switch 15 is turned on. The power switch 15 is switched through the GATE terminal, and the controller 18 controls the increase or decrease of the inductor current. A secondary winding 22 provides an output power source V _OUT for the load 30. An auxiliary winding 23 provides an operating power source V _CC to the controller 18.

Switched power supplies require a protection mechanism to prevent some abnormal conditions from occurring. A common protection is called overvoltage protection, which means that the protection of the output power supply V _OUT is too high and the protection measures may be to turn off the power switch in the switching power supply for a long time.

Figure 2 shows a commonly known overvoltage protection method. The overvoltage protection circuit in FIG. 2 is formed in the controller 18. If the comparator 32 knows that the voltage of the detected operating power supply V _CC is higher than the reference voltage V _REF1 , the overvoltage protection may be triggered. However, due to the leakage inductance, the voltage of the operating power supply V _CC does not accurately reflect the voltage of the output power supply V _OUT . Therefore, the method of Figure 2 is not accurate.

Figure 3 is another commonly known overvoltage protection method. Once the voltage of the output power supply V _OUT is higher than the voltage set by the Zener diode 38, the photo-coupler 36 pulls down the voltage at one input of the comparator 34 and triggers the overvoltage signal S. _OVP . However, Figure 3 requires an additional addition of the Kina diode 38 and the photo-coupler 36, which has a negative impact on product cost and volume.

Embodiments of the present invention provide a controller for controlling a power switch of a power supply. The power supply provides an output voltage. The controller includes a multi-function terminal, a time delay device, an over-voltage detecting device, and a gate controller. The time delay is used to provide a delay time after the power switch is turned off (OFF). The over voltage detection circuit compares the voltage of the multi-function terminal with a reference voltage to trigger an over-voltage signal after the delay time. The overvoltage signal indicates that the output voltage exceeds a predetermined value. The gate controller, when the power switch is turned on (ON), triggers the power switch to be turned off according to the voltage of the multi-function terminal. When the power switch is turned "ON", the voltage of the multi-function terminal represents the current flowing through the power switch.

Embodiments of the present invention provide a power supply. The power supply includes a transformer including a main winding and an auxiliary winding. A power switch is coupled to the main winding. A detecting resistor is coupled to the power switch and a ground power line. A controller has a multi-function terminal coupled to the detection resistor. A diode and a first resistor are connected in series between the auxiliary winding and the multi-function end.

Embodiments of the present invention provide a control method suitable for a power supply. The power supply has a power switch and provides an output voltage. When the power switch is turned on, the disable disable gate signal is triggered according to the voltage of the multi-function terminal to turn off the power switch. The voltage at the multi-function terminal represents the current flowing through an inductive component. After the power switch is turned off for a delay time, the voltage of the multi-function terminal is detected. When the voltage of the multi-function terminal is higher than a predetermined value, an over-voltage signal is triggered.

Figure 4 is an SMPS 80 implemented in accordance with the present invention. Unlike the SMPS 10 of FIG. 1, the SMPS 80 has a Zener diode 83, a diode 84, resistors 86 and 88, and a controller 82.

The controller 82 can be a single crystal integrated circuit having a multi-function terminal CS/OVP. The Zener diode 83, the diode 84 and the resistor 86 are connected in series between the auxiliary winding 23 and the multi-function terminal CS/OVP, and the resistor 88 is connected between the multi-function terminal CS/OVP and the current detecting resistor 16. The multi-function CS/OVP has at least two functions: a) current detection; and, b) overvoltage protection.

When the controller 82 enables the gate signal V _GATE , through the GATE terminal, when the power switch 15 is turned on, the voltage V _{CS of the} multi-function terminal CS/OVP indicates the current flowing through the power switch 15. At this time, the controller 82 determines when to disable the gate signal V _GATE and turns off the power switch 15 according to the voltage V _{CS of the} multi-function terminal CS/OVP.

After the power switch 15 is turned off, the voltage V _{AUX of the} auxiliary winding 23 will approximately react to the voltage of the secondary winding and also substantially reflect the voltage of the output power supply V _OUT . If the voltage V _{AUX is} lower than the voltage preset by the Zener diode 83 and the diode 84, the voltage V _{CS of} the multi-function terminal CS/OVP will be approximately 0 volts. If the voltage V _{AUX is} higher than the preset voltage, the voltage V _{CS of} the multi-function terminal CS/OVP will be a value greater than 0 volts. In order to prevent the inaccuracy caused by the leakage inductance, the controller 82 compares the voltage V _CS with a reference voltage after the power switch 15 is turned off for a delay time. If the voltage V _{CS is} higher than the reference voltage, an overvoltage signal is triggered, indicating that the voltage of the output power source V _OUT has exceeded a value corresponding to one of the voltages preset by the Zener diode 83 and the diode 84.

Figure 5 shows a portion of the controller 82 and components external to the controller 82. Fig. 6 is a signal waveform diagram in Fig. 5. The controller 82 has a time delay 54, an overvoltage detecting means 55, and a gate controller 52. The overvoltage detecting device 55 includes a sampler 56 and a comparator 50.

When the signal V _G is a logical "1", the gate signal V _GATE is also a logical "1", the power switch 15 is turned on, and the voltage V _AUX of the auxiliary winding 23 is a negative value, which is blocked by the diode 84. Therefore, it does not affect the voltage V _{CS of the} multi-function terminal CS/OVP. Therefore, the current flowing through the power switch 15 increases, and the voltage V _CS also increases, as shown in Fig. 6.

When the voltage V _CS reaches a certain level, the gate control circuit 52 turns the signal V _G to a logical "0", turning off the power switch 15. As soon as the power switch 15 is turned off, the voltage V _{AUX of the} auxiliary winding 23 initially oscillates for a short period of time and then stabilizes at a positive value which is approximately proportional to the voltage of the output power source V _OUT . The time delay 54 provides a delay time T _DELAY after the power switch 15 is turned off. The delay time T _{DELAY is} used to avoid inaccuracies caused by voltage V _AUX oscillation. After the delay time T _DELAY , the sampler 56 sends a short pulse signal V _P to sample the voltage V _CS of the multi-function terminal CS/OVP to generate a sampling signal V _SAMP . When the short pulse signal V _P is logically "0", the sampling signal V _{SAMP is} grounded and fixed to 0; when the short pulse signal V _P is logically "1", the sampling signal V _SAMP is equal to the voltage V _CS . As previously described, if the voltage of the output power source V _OUT is high, the voltage V _{AUX of the} auxiliary winding 23 is also high. Once the voltage V _{AUX of the} auxiliary winding 23 is high enough to cause the Zener diode 83 to collapse, causing the sampling signal V _{SAMP to be} higher than the reference voltage V _REF-OVP , the comparator 50 triggers the over voltage signal S _OVP . For example, the triggered voltage signal S _OVP can cause the gate controller 52 to maintain the signal _VG at a logical "0" for several consecutive switching cycles.

Figure 7 is another embodiment showing a portion of the controller 82a and components external to the controller 82a. Fig. 6 can also be the signal waveform diagram in Fig. 7. In Fig. 7, the comparator 50 and the shutter 58 can be regarded as an overvoltage detecting means. In FIG. 7, the comparator 50 compares the voltage of the multi-function terminal CS/OVP with the reference voltage V _REF-OVP to trigger the relay signal S _MED . This relay signal S _MED is obscured by the gates in the shutter 58 for most of the time, and only when the short pulse signal V _P in the shutter 58 is logically "1", the relay signal S _MED The logic level will pass as the logic level of the overvoltage signal S _OVP . Other operational principles of the embodiment of FIG. 7 can be referred to the description of FIG. 5 and will not be described again.

Figure 8 is another SMPS 80a implemented in accordance with the present invention. Unlike the SMPS 80 of FIG. 4, the SMPS 80a does not have a Zener diode 83.

In Fig. 8, after the power switch 15 is turned off, the voltage V _{CS of the} functional terminal CS/OVP approximately reflects the voltage V _{AUX of} the auxiliary winding 23 and also substantially reflects the voltage of the output power source V _OUT . Therefore, after the power switch 15 is turned off for a delay time, the controller 82 compares the voltage V _CS with a reference voltage. If the voltage V _{CS is} higher than the reference voltage, an overvoltage signal is triggered, indicating that the voltage of the output power source V _OUT has exceeded the corresponding value of the reference voltage. The internal structure of the controller 82 of Fig. 8 can be implemented in accordance with Figs. 5 and 7 or equivalent circuits. The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

10‧‧‧Switching power supply
12‧‧‧Bridge rectifier
15‧‧‧Power switch
16‧‧‧ Current Sense Resistor
18‧‧‧ Controller
20‧‧‧Transformers
22‧‧‧secondary winding
23‧‧‧Auxiliary winding
24‧‧‧ primary winding
30‧‧‧load
32, 34‧‧‧ comparator
36‧‧‧Optocoupler
38‧‧‧Kina II
50‧‧‧ comparator
52‧‧‧ gate controller
54‧‧‧Time delay
55‧‧‧Overvoltage detection device
56‧‧‧Sampling device
58‧‧‧Shader
80, 80a‧‧ ‧SMPS
82, 82a‧‧‧ controller
83‧‧‧Kina II
84‧‧‧ diode
86, 88‧‧‧ resistance
CS/OVP‧‧‧Multifunctional
S _MED ‧‧‧Relay signal
S _OVP ‧‧‧Overvoltage signal
T _DELAY ‧‧‧Delayed time
V _AUX ‧‧‧ voltage
V _CC ‧‧‧Operating power supply
V _CS ‧‧‧ voltage
V _G ‧‧‧ signal
V _GATE ‧‧‧ brake signal
V _OUT ‧‧‧output power supply
V _P ‧‧‧short pulse signal
V _REF1 ‧‧‧reference voltage
V _REF-OVP ‧‧‧reference voltage
V _SAMP ‧‧‧Sampling signal

Figure 1 is a conventional SMPS. Figures 2 and 3 show the commonly known overvoltage protection method. Figure 4 is an SMPS implemented in accordance with the present invention. Figure 5 shows a portion of the controller and components outside of the controller. Fig. 6 is a signal waveform diagram in Fig. 5. Figure 7 is another embodiment showing a portion of the controller and components external to the controller. Figure 8 is another SMPS implemented in accordance with the present invention.

12‧‧‧Bridge rectifier

15‧‧‧Power switch

16‧‧‧ Current Sense Resistor

20‧‧‧Transformers

22‧‧‧secondary winding

23‧‧‧Auxiliary winding

24‧‧‧ primary winding

30‧‧‧load

80‧‧‧SMPS

82‧‧‧ Controller

83‧‧‧Kina II

84‧‧‧ diode

86, 88‧‧‧ resistance

CS/OVP‧‧‧Multifunctional

V _AUX ‧‧‧ voltage

Claims (6)

A power supply comprising: a transformer comprising a main winding and an auxiliary winding; a power switch coupled to the main winding; a detecting resistor having a first end coupled to a grounding power line, And a second end is coupled to the power switch and one of the power controllers; a controller having a multi-function terminal coupled to the detecting resistor; and a diode and a first resistor Connected between the auxiliary winding and the multi-function terminal; wherein the power controller can detect the current flowing through the power switch through the multi-function terminal when the power switch is turned on, and pass through the multi-function terminal When the power switch is turned off, detecting whether the voltage of the multi-function terminal is higher than a reference voltage to determine whether to trigger a protection mechanism. The power supply of claim 1, further comprising a second resistor coupled between the detecting resistor and the multi-function terminal. The power supply device of claim 1, further comprising a kinetic diode, the kins diode, the diode and the first resistor are connected in series between the auxiliary winding and the multi-function end . A controller for controlling a power switch of a power supply, the power supply provides an output voltage, the controller includes: a multi-function terminal coupled to the power switch for detecting flow through the a current of the power switch; a protection detecting device, after a delay time, comparing the voltage of the multi-function terminal with a reference voltage, and triggering an excessive voltage signal when the voltage of the multi-function terminal is higher than the reference voltage; as well as A gate controller, when the power switch is turned on (ON), turns off the power switch according to the excessive voltage signal. The controller of claim 4, wherein the protection detecting device comprises: a sampler, after the delay time, sampling the voltage of the multi-function terminal to generate a sampling signal; and a comparator, The sampled signal is compared to the reference voltage. The controller of claim 4, wherein the protection detecting device comprises: a comparator that compares the voltage of the multi-function terminal with the reference voltage to trigger a relay signal; and a shutter The relay signal is masked during the delay time, and the relay signal is used as the excessive voltage signal for at least a predetermined time after the delay time.