Primary over-current protection and secondary over-voltage protection integrated power supply

Abstract

The utility model relates to a primary over-current protection and secondary over-voltage protection integrated power supply, which comprises a primary over-current protection and secondary over-voltage protection function integrated circuit, in the primary over-current protection and secondary over-voltage protection function integrated circuit, a three-pin CS of an IC1 is connected with one end of a capacitor C10, the other end of the capacitor C10 is grounded, a three-pin of the IC1 is connected with one end of a proportional divider resistor R12, and the other end of the proportional divider resistor R12 is grounded. The other end of the R12 is connected with the source electrode of the Q1 MOSFET, one end of the other divider resistor R13 is connected with the third pin of the IC1, the other end of the R13 is connected with the negative electrode of the diode D06, the positive electrode of the diode D06 is connected with one end of the auxiliary winding, and the other end of the auxiliary winding is grounded. According to the utility model, the CS end of the IC1 is used for monitoring the output voltage in real time, and the switch working state of the Q1 is closed when the voltage signal exceeds the preset maximum value, so as to form secondary overvoltage protection.

Description

Technical Field

[0001] The utility model belongs to the technical field of power supply, and particularly relates to a primary overcurrent protection and secondary overvoltage protection integrated power supply. Background Art

[0002] With the widespread application of power products, the market demand is increasing, and the use of switching power supplies is becoming more and more widespread. Power supplies are constantly updated and iterated with the ever-changing market demand; industry insiders pointed out that in the past two years, the update cycle of power supplies has changed from two-year iterations to one-year iterations of switching power supplies, and more innovative functions are needed to meet the requirements of market customers. The demand for miniaturization has always been the trend. Different switching converter circuits are aimed at different power levels. In the field of miniaturized power supplies, flyback switching power supplies are the most common and are widely used in the field of industrial control. The protection function of the power supply is crucial to the stable operation of industrial control equipment. Utility Model Content

[0003] The utility model aims to solve the problem that the power supply in the prior art lacks protection functions and provides an integrated power supply with primary overcurrent protection and secondary overvoltage protection. The specific technical solution is as follows:

[0004] A primary overcurrent protection and secondary overvoltage protection integrated power supply includes a primary overcurrent protection and secondary overvoltage protection function integrated circuit, in which the three-pin CS of IC1 is connected to one end of a capacitor C10, the other end of C10 is grounded, the 3rd pin of IC1 is connected to one end of a proportional voltage divider resistor R12, the other end of R12 is connected to the source of Q1MOSFET, one end of another voltage divider resistor R13 is connected to the 3rd pin of IC1, the other end of R13 is connected to the cathode of diode D06, the anode of diode D06 is connected to one end of an auxiliary winding, and the other end of the auxiliary winding is grounded; the IC1 shuts down the working state of Q1 in an overvoltage state to achieve protection.

[0005] As a further technical solution of the present invention, the IC1 enters an overvoltage state when an OVP event is detected for 10 consecutive cycles.

[0006] As a further technical solution of the utility model, in the integrated circuit of primary overcurrent protection and secondary overvoltage protection functions, one end of the overcurrent resistor R10 is connected to the source of the Q1 MSAFET, and the other end of R10 is grounded, pin 2 FB of IC1 is connected to pin 4 of the photocoupler PC1, pin 3 of the photocoupler is grounded, capacitor C11 is connected in parallel between pins 3 and 4 of the photocoupler, pin 6 VCC of IC1 is connected to one end of the resistor R02, the other end of R02 is connected to one end of the resistor R11, the other end of R11 is connected to the cathode of the diode D3, the positive electrode of D3 is connected to one end of the auxiliary winding, the positive electrode of the capacitor C8 is connected to one end of R02, the other end of the negative electrode of C8 is grounded, C9 is connected at both ends of C8, the negative electrode of the voltage regulator DZ1 is connected to one end of C9, and the positive electrode of DZ1 is grounded.

[0007] The beneficial effects of the utility model are as follows:

[0008] In the present application, the CS terminal of IC1 is used to monitor the output voltage in real time, and when the voltage signal exceeds the preset maximum value, the switch working state of Q1 is turned off to form secondary overvoltage protection; and the overvoltage protection state is released until the fault is eliminated and the internal latch of IC1 is reset.

[0009] In this application, the CS terminal of IC1 is used to monitor the primary current of the power supply in real time. When the current between the drain and source of Q1 is too large, IC1 will limit the pulse current one by one and adjust the duty cycle pulse width to implement the hiccup protection mode until the overcurrent fault is eliminated and the normal output state can be restored by itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A circuit diagram of a primary overcurrent protection and secondary overvoltage protection integrated power supply is shown;

[0011] Figure 2 shows a schematic diagram of a flyback converter;

[0012] Figure 3 A schematic diagram showing the current flow of a flyback converter is shown;

[0013] Figure 4 shows a schematic diagram of the structure of IC1;

[0014] Figure 5 The schematic diagram of the output overvoltage protection principle is shown;

[0015] Figure 6 The schematic diagram of the structure of the integrated circuit of primary overcurrent protection and secondary overvoltage protection function is shown. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the embodiments of the present utility model clearer, the technical solution of the present utility model will be clearly and completely described below in conjunction with the embodiments.

[0017] Figure 1 A circuit diagram of a primary overcurrent protection and secondary overvoltage protection integrated power supply is shown; Figure 1 In the present invention, the primary overcurrent protection and secondary overvoltage protection integrated power supply includes a primary filter rectifier circuit, a switch conversion circuit, a secondary filter rectifier circuit, a secondary adjustment circuit and an integrated circuit with primary overcurrent protection and secondary overvoltage protection functions, wherein the primary filter rectifier circuit, the switch conversion circuit, the secondary filter rectifier circuit and the secondary adjustment circuit are all prior arts, and this application does not provide protection for them, nor does it elaborate on them.

[0018] Figure 2 shows a schematic diagram of a flyback converter; Figure 2 In Figure 1, the flyback converter is based on a coupled inductor T, which, in addition to helping with power conversion, also provides isolation between the converter's input and output; otherwise, it has the same basic elements as other switching converter topologies: two switches (MOSFET Q and diode D) and an output capacitor C. The charge stored in the output capacitor C is responsible for keeping the voltage at the load stable.

[0019] Figure 3 A schematic diagram showing the current flow of a flyback converter is shown; Figure 3During TOFF, the MOSFET is turned off and the coupled inductor begins to demagnetize through the diode (the diode is now directly polarized); then, the inductor current charges the output capacitor and powers the load, and the charge stored in the output capacitor C is responsible for keeping the voltage on the load stable; the flyback topology requires a power management chip to implement its functions. This application uses the LD5760, which is an energy-saving green power PWM control chip. It is suitable as the main control chip of a 100W-150W flyback power supply to share the same circuit to achieve primary overcurrent protection and secondary overvoltage protection. It has many novel functions and features. The PWM controller LD5760 is a green mode PWM IC with built-in input / output functions in SOP-7 or SOP-8 packages. Therefore, the device can minimize the number of components (power supply miniaturization), circuit space, and reduce the overall material cost of power applications. The LD5760 has HV startup, green mode power saving operation and internal slope compensation, soft start function to minimize power consumption and improve system performance. LD5760 has complete protection functions such as OLP (overload protection), OVP (overvoltage protection), fast SCP (short circuit protection) and over-undervoltage input / output overvoltage protection to prevent the circuit from being damaged under abnormal conditions; it has the following characteristic parameters: high voltage (650V) startup circuit; no-load power consumption <30mW at 230VAC; built-in Brown input / output function on HV pin; built-in X-Cap discharge on HV pin; frequency exchange to improve EMI; non-sound noise green mode control; LEB (leading edge blanking) on ​​CS pin; internal slope and OCP compensation; OVP (overvoltage protection) on VCC / CS; OLP (overload protection); OTP (overtemperature protection); SCP (short circuit protection); soft start and soft start; +300mA / -800mA driving capability; In addition, LD5760 has frequency exchange and soft drive functions to minimize noise and improve EMI current continuous switching mode, because there is no reverse recovery loss on the diode and the MOSFET is soft-turned on, its efficiency is high.

[0020] Figure 4 shows a schematic diagram of the structure of IC1; Figure 4 In this application, the PWM control chip model LD5760 is used to realize the primary over-current protection and secondary over-voltage protection functions of the same circuit; Figure 4In the figure, the PWM control chip model is LD5760; it has seven pins, 1-pin OTP (overtemperature protection); 2-pin feedback input terminal; 3-pin current detection terminal; 4-pin ground terminal; 5-pin switch tube drive terminal; 6-pin chip power supply terminal; 8-pin chip start terminal; according to the characteristics of the chip, it can share the same circuit to realize primary overcurrent protection and secondary overvoltage protection functions, and the power supply will automatically restore normal output after the fault is removed. The primary overcurrent protection and secondary overvoltage protection are shared in the same circuit at the current detection terminal of pin 3. CS current detection, leading edge blanking and negative spikes on the CS pin. Typical current mode PWM controller feedback, current signal and voltage signal can close the control loop to achieve regulation. LD5760 detects the primary MOSFET current at both ends of the CS pin and controls it in peak current mode and limits the pulse-by-pulse current. The current detection pin with the maximum voltage threshold is set to 0.7V. Therefore, the MOSFET peak current can be calculated as IPEAK=0.7 / RS (RS is the overcurrent detection resistor). A 300nS leading edge blanking (LEB) time is also designed in the input of the CS pin to prevent false protection action caused by current spikes. In low-power applications, if the pulse width of the total turn-on spike is less than 150nS and the negative spike on the CS pin does not exceed -0.3V, the current spike can be eliminated freely with an RC filter. This is to achieve the primary overcurrent protection function through the primary current detection resistor.

[0021] Figure 5 The schematic diagram of the output overvoltage protection principle is shown; Figure 5 In the LD5760, the CS current sensing terminal can also realize the function of output overvoltage protection; the output overvoltage protection is realized on the LD5760, the auxiliary winding voltage is reflected to the secondary winding, and the flat voltage on the CS pin is proportional to the output voltage. The LD5760 uses a voltage divider resistor to sample the inductive auxiliary voltage and the flat voltage on the CS pin. The sampled voltage level performs output overvoltage protection after a delay. This delay time is used to ignore the voltage ringing caused by leakage inductance. The sampled voltage level is compared with the internal threshold voltage VCSOVP. If the sampled voltage exceeds the OVP (output overvoltage protection) trip level, an internal counter starts counting subsequent OVP (output overvoltage protection) events. This adds a counter to prevent incorrect OVP (output overvoltage protection). Detection events that may occur during ESD or lightning. However, if an OVP (output overvoltage protection) event is detected for a subsequent period of typically 10 cycles, the OVP (output overvoltage protection) circuit turns off the MOSFET. The converter only restarts when the protection is locked.

[0022] Figure 6The schematic diagram of the structure of the integrated circuit of primary overcurrent protection and secondary overvoltage protection function is shown; wherein, the three-pin CS of the IC1 is connected to one end of the capacitor C10, the other end of the C10 is grounded, the 3rd pin of the IC1 is connected to one end of a proportional voltage-dividing resistor R12, the other end of the R12 is connected to the source of the Q1MOSFET, one end of another voltage-dividing resistor R13 is connected to the 3rd pin of the IC1, the other end of the R13 is connected to the cathode of the diode D06, the anode of the diode D06 is connected to one end of the auxiliary winding, and the other end of the auxiliary winding is grounded; the output overvoltage protection function can be realized by the CS detection function; specifically, the auxiliary winding of T1 is connected to the diode D06 in series with the resistors R13 and R12, R10 to form a voltage-dividing function, and the voltage signal after the voltage division is transmitted to the CS end of IC1. When the output voltage suddenly increases, the voltage on the auxiliary winding also increases accordingly. The voltage signal obtained by the above voltage division exceeds the maximum setting threshold of VCSOVP inside IC1, and the power supply will directly enter the output overvoltage protection state, with 10 cycles as the protection count mode to prevent false triggering; after triggering, IC1 turns off the switch working state of the power tube Q1, the protection is locked, and the power supply has no output. Only when the fault is eliminated and the internal latch of IC1 is reset, the overvoltage protection state is released.

[0023] One end of the overcurrent resistor R10 is connected to the source of the Q1 mosfet, and the other end of R10 is grounded, the 2nd pin FB of IC1 is connected to the 4th pin of the photocoupler PC1, the 3rd pin of the photocoupler is grounded, the capacitor C11 is connected in parallel between the 3rd and 4th pins of the photocoupler, the 6th pin VCC of IC1 is connected to one end of the resistor R02, the other end of R02 is connected to one end of the resistor R11, the other end of R11 is connected to the cathode of the diode D3, the anode of D3 is connected to one end of the auxiliary winding, the anode of the capacitor C8 is connected to one end of R02, the other end of the anode of C8 is grounded, C9 is connected to both ends of C8, the cathode of the voltage regulator DZ1 is connected to one end of C9, and the anode of DZ1 is grounded; the resistor R10 is the primary current of the power supply Detection resistor, when the current between the drain and source of Q1 is too large, the voltage on R10 rises, and passes the voltage signal to the CS (current detection) port of IC1 after passing through the RC filter composed of resistor R12 and capacitor C10. The VCSmax threshold of the CS port is 0.7V; when the voltage signal on CS exceeds this threshold, IC1 will limit the pulse current one by one and adjust the duty cycle pulse width; realize the hiccup protection mode (the power supply enters the protection state as soon as it is started, and it is a state of cyclic starting and stopping the output) until the overcurrent fault is eliminated and the normal output state can be restored by itself.

[0024] The above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it.

Claims

1. A primary overcurrent protection and secondary overvoltage protection integrated power supply, including a primary overcurrent protection and secondary overvoltage protection function integrated circuit, characterized in that: In the integrated circuit of primary overcurrent protection and secondary overvoltage protection functions, the three-pin CS of IC1 is connected to one end of capacitor C10, the other end of C10 is grounded, the 3rd pin of IC1 is connected to one end of a proportional voltage divider resistor R12, the other end of R12 is connected to the source of Q1 MOSFET, one end of another voltage divider resistor R13 is connected to the 3rd pin of IC1, the other end of R13 is connected to the cathode of diode D06, the anode of diode D06 is connected to one end of the auxiliary winding, and the other end of the auxiliary winding is grounded; the IC1 shuts down the working state of Q1 in an overvoltage state to achieve protection.

2. The integrated power supply with primary overcurrent protection and secondary overvoltage protection according to claim 1, characterized in that: The IC1 enters an overvoltage state when an OVP event is detected for 10 consecutive cycles.

3. The integrated power supply with primary overcurrent protection and secondary overvoltage protection according to claim 2, characterized in that: In the integrated circuit of primary overcurrent protection and secondary overvoltage protection functions, one end of the overcurrent resistor R10 is connected to the source of the Q1 MSAFET, and the other end of R10 is grounded, pin 2 FB of IC1 is connected to pin 4 of the photocoupler PC1, pin 3 of the photocoupler is grounded, capacitor C11 is connected in parallel between pins 3 and 4 of the photocoupler, pin 6 VCC of IC1 is connected to one end of the resistor R02, the other end of R02 is connected to one end of the resistor R11, the other end of R11 is connected to the cathode of the diode D3, the anode of D3 is connected to one end of the auxiliary winding, the anode of the capacitor C8 is connected to one end of R02, the other end of the anode of C8 is grounded, C9 is connected at both ends of C8, the cathode of the voltage regulator DZ1 is connected to one end of C9, and the anode of DZ1 is grounded.

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