The use of MP 3 blocks in modern TVs. Schematic diagram of a switching power supply for a TV. Surge filter for power supply unit

Chapter 3. Schemes of switching power supplies.

In this article we will consider a scheme in which key management is done according to a different principle. This scheme, with minor changes, is used in many TVs, such as Akai CT-1405E, Elekta CTR-2066DS and others.

A comparison device is assembled on transistor Q1; its circuit is no different from others discussed earlier. Only used here npn transistor, as a result, the switching polarity changed. The comparison circuit is powered from a separate winding from the rectifier D5 with filter C2. The initial bias to switch Q4 is supplied through resistor R7, which is usually several resistors connected in series, which is apparently explained by better heat transfer, the elimination of breakdown between the terminals (after all, the voltage drop across it is 300 V) or the manufacturability of the assembly. I myself don’t know why this is done, but in imported equipment you see this all the time.

The feedback circuit is connected here in a different way than we discussed earlier. One terminal of the feedback winding is connected as usual, to the base of the key, and the other to the diode distributor D3, D4.

What is the result? Transistors Q2 and Q3, which are a composite transistor, are adjustable resistance. This resistance (between the positive of capacitor C3 and the emitter of Q3) depends on the error signal coming from Q1. Since transistor Q2 has p-n-p conductivity, with an increase in the voltage coming to its base, its current decreases, transistor Q3 closes, that is, the resistance of the composite transistor increases. This property of the circuit is used.

Let's consider the moment of launch. Capacitor C3 is discharged. The feedback circuit is connected by plus to the base, minus through D4 and R9 with a common wire. There is a process of linear increase in the collector current, which ends with the switch being saturated and closing. In this case, the polarity of the voltage on the feedback winding is reversed and this voltage charges capacitor C3 through diode D3. When the energy of the transformer is used up, capacitor C3 will be connected to the base-emitter junction of the switch through the resistance of the composite transistor with a minus to the base and closes the switch.

The discharge time of C3 and the value of the closing potential depend on the resistance value of the composite transistor. At the moment the power supply starts, this resistance is large and the discharge of capacitor C3 does not delay the next cycle, however, in steady state, the delay of the next cycle is sufficient to regulate the average power supplied to the load. Thus, we see that the circuit in question is not exactly PWM. If in previous schemes the time of the open state of the key was subject to regulation, then in this scheme the time of the closed state of the key is regulated.

Fig 2

The figure shows the discharge path of capacitor C3. At time t0, the switch collector current begins to increase and continues until time t1. During this period of time, the voltage Ube of the key increases. This does not affect the charge of C3 in any way, since C3 is connected to the feedback winding through diode D3, which is closed at this moment. As soon as the increase in the collector current of the switch ends, the polarity of the voltage on the feedback winding changes to reverse, diode D3 opens and charging C3 begins. At the same time, through the resistance of the composite transistor Rstate, this voltage is applied to the base-emitter junction of the switch, reliably locking it. Charge C3 continues until time t2, that is, until the accumulated energy of the transformer is transferred to the load. At this moment, charged C3 through Rstate and the opened diode D4 will be connected to the base-emitter junction of the switch. The figure below shows how the voltage of the charged capacitor C3 is divided between the resistance of the composite transistor Rcomp (Ucomp) and the resistance of the base-emitter section of the switch Rcl (Ube), which is determined by the sum of the resistances R9 and the resistance of the open diode D4. The resistance of resistors R6, R9 and R10 is small and can be ignored. With a high resistance Rstate, the discharge of C3 occurs more slowly and the threshold for opening the key will be reached later than with a low Rstate. At time t3, voltage C3 will decrease to such a value that the locking voltage at the base of the key will disappear and the cycle will repeat. So the resistance of the composite transistor participates in the process.

Schemes of domestic switching power supplies.

The vast majority of domestic UPS circuits are built according to the same circuit, according to the same principle, and differ only in the startup circuit and the output voltage values ​​of the secondary rectifiers. And one more feature - domestic UPSs are not designed to operate in standby mode (that is, in almost idle mode). All UPSs have overload protection and short circuit under load, from undervoltage in the network below 160 V, idle. On some models with remote control The UPS is turned off using an artificially created overload; in this case, the overload protection is triggered and generation is disrupted.

Since there are still a lot of domestic TVs with such UPSs, I will talk about them in more detail, despite the fact that I will repeat myself in some areas. What I will talk about applies to all UPS models built on discrete elements. We will consider domestic UPSs built using the K1033EU1 microcircuit (analogous to TDA4601) in the next chapter, in which I will describe the operation of UPS on microcircuits. I will not consider newer UPSs that use developments from foreign manufacturers here.

Schematic diagram of the MP-3-3 power module

Let's look at the circuit diagram of the MP-3-3 power module. The module includes a low-voltage rectifier (diodes VD4-VD7), a trigger pulse shaper (VT3), pulse generator(VT4), stabilization device (VT1), protection device (VT2), pulse transformer T1, diode rectifiers VD12-VD15, voltage stabilizer 12 V (VT5-VT7).

Fig 3

The pulse generator is assembled according to a self-oscillator circuit with collector-base connections on a VT4 transistor. When you turn on the TV constant pressure from the output of the network rectifier filter (capacitors C16, C19, C20) through winding 19-1 of transformer T1 it is supplied to the collector of transistor VT4. At the same time, the mains voltage from diode VD7 through resistors R8 and R 11 charges capacitor C7, and is also supplied to the emitter of transistor VT2, where it is used in the device for protecting the power module from low mains voltage. When the voltage across capacitor C7 applied between the emitter and base 1 of unijunction transistor VT3 reaches 3 V, transistor VT3 opens. Capacitor C7 begins to discharge along the circuit: emitter-base junction of transistor VT3, emitter junction of transistor VT4, parallel connected resistors R14 and R16, capacitor C7.

The discharge current of capacitor C7 opens transistor VT4 for a time of 10...15 μs, sufficient for the current in its collector circuit to increase to 3...4 A. The flow of the collector current of transistor VT4 through the magnetization winding 19-1 is accompanied by the accumulation of energy in the magnetic field core. After capacitor C7 has finished discharging, transistor VT4 closes. The cessation of the collector current causes the appearance of a self-induction emf in the coils of transformer T1, which creates a positive voltage at terminals 6, 8, 10, 5 and 7 of transformer T1. In this case, current flows through the diodes of the half-wave rectifiers in the secondary circuits VD12-VD15.

With a positive voltage at terminals 5, 7 of transformer T1, capacitors C14 and C6 are charged, respectively, in the anode and control electrode circuits of thyristor VS1 and C2 in the emitter-base circuit of transistor VT1.

Capacitor C6 is charged through the circuit: pin 5 of transformer T1, diode VD11, resistor R 19, capacitor C6, diode VD9, pin 3 of the transformer. Capacitor C14 is charged through the circuit: pin 5 of transformer T1, diode VD8, capacitor C14, pin 3 of transformer. Capacitor C2 is charged through the circuit: pin 7 of transformer T1, resistor R13, diode VD2, capacitor C2, pin 13 of the transformer.

The subsequent switching on and off of transistor VT4 of the autogenerator is carried out similarly. Moreover, several such forced oscillations are sufficient to charge the capacitors in the secondary circuits. With the completion of charging of these capacitors between the windings of the autogenerator connected to the collector (pins 1, 19) and to the base (pins 3, 5) of the VT4 transistor, a positive voltage begins to operate Feedback. In this case, the self-oscillator goes into self-oscillation mode, in which transistor VT4 will automatically open and close at a certain frequency.

In the open state of transistor VT4, its collector current flows from the plus of capacitor C16 through the winding of transformer T1 with pins 19, 1, the collector and emitter junctions of transistor VT4, parallel connected resistors R14, R16 to the minus of capacitor C16. Due to the presence of inductance in the circuit, the collector current increases according to a sawtooth law.

To eliminate the possibility of failure of transistor VT4 from overload, the resistance of resistors R14 and R16 is selected in such a way that when the collector current reaches 3.5 A, a voltage drop is created across them sufficient to open thyristor VS1. When the thyristor opens, capacitor C14 is discharged through the emitter junction of transistor VT4, resistors R14 and R16 connected in parallel, and open thyristor VS1. The discharge current of capacitor C14 is subtracted from the base current of transistor VT4, and the transistor closes prematurely.

Further processes in the operation of the autogenerator are determined by the state of the thyristor VS1. Opening it earlier or later allows you to regulate the rise time of the sawtooth current and thereby the amount of energy stored in the transformer core.

The power module can operate in stabilization mode and short circuit mode.

The stabilization mode is determined by the operation of the UPT on transistor VT1 and thyristor VS1. At a mains voltage of 220 V, when the output voltages of the secondary power supplies reach rated values, the voltage on the winding of transformer T1 (pins 7, 13) will increase to a value at which the constant voltage at the base of the transistor VT1, where it is supplied through the divider R1-R3, becomes more negative than at the emitter, where it is completely transmitted. Transistor VT1 opens along the circuit: pin 7 of the transformer, R13, VD2, VD1, emitter and collector junctions of transistor VT1, R6, control electrode of thyristor VS1, R14-R16, pin 13 of the transformer. The transistor current, summed with the initial current of the control electrode of the thyristor VS1, opens it at the moment when output voltage module reaches nominal values, stopping the increase in collector current.

By changing the voltage at the base of transistor VT1 with trimming resistor R2, you can adjust the voltage across resistor R10 and, therefore, change the opening moment of thyristor VS1 and the duration of the open state of transistor VT3, i.e., set the output voltages of secondary power supplies.

As the network voltage increases (or the load current decreases), the voltage at terminals 7, 13 of transformer T1 increases. This increases the negative base voltage relative to the emitter of transistor VT1, causing an increase in the collector current and a voltage drop across resistor R10. This leads to earlier opening of thyristor VS1 and closing of transistor VT4, the power supplied to the secondary circuits decreases.

When the network voltage decreases (or the load current increases), the voltage on the transformer winding Tl and the potential of the base of the transistor VT1 relative to the emitter become correspondingly less. Now, due to a decrease in the voltage created by the collector current of transistor VT1 on resistor R10, thyristor VS1 opens at a later time and the amount of energy transferred to the secondary circuits increases.

A significant role in protecting transistor VT4 is played by the cascade on transistor VT2. When the network voltage decreases below 150 V, the voltage on winding T1 with pins 7, 13 is insufficient to open transistor VT1. In this case, the stabilization and protection device does not work and the possibility of overheating of the VT4 transistor due to overload is created. To prevent the failure of transistor VT4, it is necessary to stop the operation of the autogenerator. The transistor VT2 intended for this purpose is connected in such a way that a constant voltage is supplied to its base from the divider R18, R4, and a pulsating voltage with a frequency of 50 Hz is supplied to the emitter, the amplitude of which is stabilized by the zener diode VD3. When the network voltage decreases, the voltage at the base of transistor VT2 decreases. Since the voltage at the emitter is stabilized, a decrease in the voltage at the base causes the transistor to open. Through the open transistor VT2, trapezoidal pulses from the diode VD7 reach the control electrode of the thyristor, opening it for a time determined by the duration of the trapezoidal pulse. This stops the generator from working.

Short circuit mode occurs when there is a short circuit in the load of secondary power supplies. In this case, the module is started by triggering pulses from the trigger device (transistor VT3), and turned off using thyristor VS1 according to the maximum collector current of transistor VT4. After the end of the trigger pulse, the device is not excited, since all the energy is consumed by the short-circuited circuit.

After the short circuit is removed, the module enters stabilization mode.

Pulse voltage rectifiers connected to the secondary winding of transformer T1 are assembled using a half-wave circuit.

The VD12 diode rectifier creates a voltage of 130 V to power the horizontal scanning module. The ripples of this voltage are smoothed out by capacitor C27. Resistor R22 eliminates the possibility of a significant increase in voltage at the rectifier output when the load is turned off.

A 28 V voltage rectifier is assembled on the VD13 diode, designed to power the module personnel scan. The filter at its output is formed by capacitor C28 and inductor L2.

The 15 V voltage rectifier for powering the ultrasonic sounder is assembled using a VD15 diode and a C30 capacitor.

The 12 V voltage used in the control unit, color module, radio channel module and vertical scan module is created by a rectifier using diode VD14 and capacitor C29. A compensation voltage stabilizer is included at the output of this rectifier. It consists of a regulating transistor VT5, a current amplifier VT6 and a control transistor VT7. The voltage from the output of the stabilizer through the divider R26, R27 is supplied to the base of the transistor VT7. Variable resistor R27 is designed to set the output voltage. In the emitter circuit of transistor VT7, the voltage at the output of the stabilizer is compared with the reference voltage at the zener diode VD16. The voltage from the collector VT7 through the amplifier on the transistor VT6 is supplied to the base of the transistor VT5, connected in series to the rectified current circuit. This leads to a change in its internal resistance, which, depending on whether the output voltage has increased or decreased, either increases or decreases. Capacitor C31 protects the stabilizer from excitation. Through resistor R23, voltage is supplied to the base of transistor VT7, which is necessary to open it when turned on and restore it after a short circuit. Choke L3 and capacitor C32 are an additional filter at the output of the stabilizer.

IMP-3-3 Charger from the power supply of an old TV. Don't throw away your old TV, its power supply will still serve you! We start the power supply from an old TV, increase its output to 7 Amperes, at a voltage of 15 Volts. The resulting unit is more suitable for charging batteries and conducting small experiments.

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Review of one of the many Chinese mp3 modules. This one can switch folders and play flac, bluetooth and FM radio are also available.

Module brand ct02ea. Plays mp3 and flac from flash drives, memory cards and external hard drives. There is a linear input, output, and a built-in amplifier for speakers. There is bluetooth, it plays an audio signal from the phone, you can use buttons on the remote control/front panel to switch tracks on the phone, there is a speakerphone, when incoming call pronounces the phone number in English. language. There is a radio with good sensitivity.

The front panel contains: an LED display that shows the track number, the frequency of the radio station and additional operating mode icons; USB connector for connecting media; memory card slot; audio output (jack 3.5); audio input (mini usb), slide switch and control buttons

Top view: the microphone on the wires is visible. The device can work via Bluetooth as a speakerphone. Two connectors for speakers and a power connector. Attention, this module is powered by 5V!


back side

Board with front panel removed. On the board there is an inscription: JLZ02EBT A Google search did not give any results.

Display appearance. The display itself is LED, dynamic indication is used. The segments are connected back-to-back in parallel; thanks to this connection, the indicator is connected to the controller with only 7 pins. On the right is the IR receiver for the remote control.

Elements on the board. Everything is based on the AC1624 controller. I don’t remember the name of the manufacturer right now. They have a carload of similar controllers and a small cart. It feels like the manufacturer releases a new title almost every day. In this case, FM radio is already integrated inside. Two 8002b microcircuits are audio amplifiers, one microcircuit per channel. 25d80 - flash memory chip with device firmware. The small blue scarf is a bluetooth module. Unsoldered connectors: linear inputs/outputs and power supply, everything is labeled on the back of the board, routed directly to the connectors on the front panel.

Test bench: power from a laboratory unit, speakers from some kind of monoblock, external HDD. On the indicator there are symbols of an extraterrestrial civilization - features of a dynamic display; at each moment only a few segments are illuminated, due to the inertia of vision we see the full picture.

Current consumption. Medium volume, plays mp3 with hard drive. On average about 0.7A

Playing from a flash drive, some album was recorded on it in flac format.

Current consumption when playing from a flash drive. Average 0.4A

A short video demonstrating the main functions

Switching operating modes is announced in English. When power is applied, the module is in Bluetooth mode by default. If you turn it off/on using the remote control, it will be in the same mode as before it was turned off. Remembers the volume level and the file being played.
I was very pleased to work with external drive. I connected a 500GB hard drive formatted in extFAT. I threw several folders with music there. Folders can only be switched from the remote control by long pressing the track_forward/track_backward buttons.
If Bluetooth is connected, the connection is disconnected when switching modes. Can work with voice calls - the microphone sensitivity is not great, but overall not bad.
The quality of playback under test conditions was difficult to assess, but overall not bad. I didn't hear any obvious distortions. To complete the picture, you need to test the device with normal acoustics.
There is a repeat and random play mode.
Radio. It seems to be there, the sensitivity is not bad. But the setup is inconvenient. It looks like the module is scanning the airwaves and recording broadcast frequencies into memory. In the video you can see how it is configured. The receiver was the last thing I was interested in (I don’t need it at all), so I didn’t really look into it.
The module is powered by 5V, I would recommend a power source with a current of at least 1.5A, especially if a USB hard drive is used.

I'm planning to buy +48 Add to favorites I liked the review +34 +62

Not bad Charger with good output characteristics can be made from old TVs with pulsed power supplies such as MP1, MP3-3, MP403, etc. Minor modification of the unit allows it to be used for charging battery with current up to 6-7A, repair of car radios and other equipment.

Battery charger from MP3-3

The whole point of remaking the block is to increase the load capacity of TPI and rectifier diodes, for this we connect windings with pins 12,18 and 10,20 in parallel, pin 20 is connected to the common pin of secondary sources (12), and pin 10 is connected to pin 18, rectifier diodes 12V and 15V turn it off and connect a diode with a current of 10-25A to pins 10, 18, which must be installed on a heat sink; for these purposes I used a heat sink from a standard 12 V stabilizer.

Details of which are unnecessary you can remove it from the board (except for the so-called outlet), you can put a new diode on it, connect a 470 pf capacitor in parallel to it and at the output electrolyte 470 uF x 40 V, parallel to it we put a load resistor MLT 2 with a nominal value of 510-680 ohms and a ceramic capacitor at 1 µF, these parts are installed to prevent the appearance of high-frequency voltage at the output of the power supply.

To adjust the output voltage You can use trimming resistor R2 according to the circuit, which is soldered off and instead of it we connect an external variable wire resistor of the PPZ type 1-1.5 kohm, adjusting the output voltage from 13V to 18V.

To put the block into mode To stabilize it, you need to load it; for this you can use a lamp from the refrigerator, connecting it to pins 6 and 18.

In your loading block I used the +28 V output, connecting to it a 28 V 5W lamp, which simultaneously serves as a backlight for the voltmeter scale with an extended scale from “five”. The unit heats up under load as in normal mode, but it will be better if you make forced airflow by installing a cooler from the computer.
When connecting the battery, it is necessary to observe the polarity and install a 10A fuse at the output.

TVs of the USCT series are gradually losing ground, and often a completely serviceable TV, but with a used kinescope, is thrown away. There is no point in convincing readers of how much wonderful devices can be made from the parts of this “poor fellow”.

One of the most interesting TV units of this type - pulse source power supply, quite light and compact, being in good condition, giving good output characteristics. This article describes how to make a power source based on the MP-3-3.

If you have been involved in the repair of USCT, you should know that if the MP-3-3 is simply plugged into the network without load, it does not work. A protection system is triggered, which monitors not only overload, but also “underload”. Therefore, in order for the MP-3-3 to be used as a laboratory one, that is, with a wide variety of loads, it needs to be loaded.

In L.1 it is proposed to load each of the MP-3-3 output sources with starting loads, but, as practice shows; this is not necessary. The fact is that the protection system does not monitor the currents in all secondary windings of the pulse transformer.

It is important for her that the block is loaded via the secondary circuit. And it doesn’t matter which secondary circuit. In addition, to bring the source to stabilization mode, it is necessary to load it with at least 20 W, and with the resistor resistances indicated in L.1, the total is no more than 3-4 W. To bring the source to operating mode, this is not enough.

The pulse generator of a working MP-3-3 source is switched off when the load power is less than 15-20W. Therefore, we take the most unnecessary 135V output and load it with a power of about 20-25L/, simply by connecting an incandescent lighting lamp from the refrigerator to its output. Or a wirewound resistor of the "PEV" type for 600-800 Ohms with a power of 20-30W.

With such a load, the source goes into stabilization mode. Now you can use its outputs with voltages of 28V (up to 1 A), MU (up to 2 A), 15V (up to 2 A). How to use them depends on what voltages you plan to receive from the source.

Rice. 1. Fragment of the MP-3-3 power supply circuit.

You can replace all secondary circuits with others, replace the 12V transistor stabilizer with an adjustable integral one, use it on all outputs adjustable stabilizers etc. It should be noted that a separate transformer winding is used for the 15V output; this will make one of the outputs galvanically isolated from the others.

And perhaps the most unexpected application of the MP-3-3 is that after modifying the output circuits, even a small tube UMZCH can be powered from it, using an output voltage of 135V to power its anode circuits.

Karavkin V. Rk2005, 1.

Literature:

  1. Kashkarov A. Power supply from a TV. and. Radiomir 9, 2004.
  2. S.A. Elyashkevich. Color TVs ZUSTST.