High Power Factor Controller TDA4862/63 and Its Application-EEWORLD

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1. Introduction

TDA4862 is a high power factor controller launched by Siemens AG, Germany, and TDA4863 is an enhanced version of TDA4862. In April 1999, Infineon Technologies AG was established in Munich, Germany as a wholly-owned subsidiary of Siemens AG, Germany, and all of Siemens' semiconductor businesses were transferred to Infineon Technologies. Now, Infineon Technologies has become one of the top ten semiconductor manufacturers in the world. TDA4862 and TDA4863 are now produced by Infineon Technologies.
The following introduces the features, pin functions, electrical parameters, working principles and typical applications of TDA4862 and TDA4863 high power factor controllers.

2. Features and Pin Description

2.1 Features

For ease of comparison, the features of TDA4862 and TDA4863 are listed in Table 1.

2.2 Pin Description

TDA4862 and TDA4863 are both packaged in PDIP-8 and PDSO-8. This article mainly introduces the PDIP-8 pin package, and its pin arrangement is shown in Figure 1.

The pin functions of TDA4862 and TDA4863 are as follows:
·VSENSE (pin 1): voltage amplifier inverting input. This terminal is connected to the output of the boost converter through a resistor divider. Pin 2 is connected to this terminal through a feedback capacitor to form a feedback compensation network;
·VAOUT (pin 2): voltage amplifier output. This terminal is connected to one input of the multiplier inside the controller. To prevent input voltage overshoot, this terminal is internally connected to a 5V clamp circuit. When the input voltage is lower than 2.2V, the drive output circuit will be disabled. If the current flowing into this terminal exceeds the threshold, the output signal of the multiplier will drop to prevent the boost power MOSFET from being damaged due to overvoltage fault.
·MULTIN (pin 3): another input of the multiplier. This terminal is connected to the full-wave rectified output voltage through a resistor divider.
·ISENSE (pin 4): current detection signal input. This terminal is connected to the inverting input of the current detection comparator inside the controller, and the source current of the boost power MOSFET is controlled through an external detection resistor. To prevent negative input voltage from affecting the controller, this terminal is internally clamped at -0.3V. In addition, to suppress the voltage spike introduced by the turn-on of the boost power MOSFET, the current detection signal input terminal of the TDA4862 is internally connected to a low-pass filter network, while the TDA4863 adds a rising edge blanking circuit.
·DETIN (pin 5): zero current detector input terminal. This terminal realizes zero-crossing monitoring of the inductor current through the boost inductor auxiliary winding.
·GND (pin 6): signal ground. A bypass capacitor should be connected between VCC and this terminal.
·GTDRV (pin 7): drive output terminal. This terminal is the output terminal of the high-current totem pole drive circuit, with an internal clamp network, which can directly drive the power MOSFET. An active clamp circuit is added to the TDA4863 to ensure that the output signal at this terminal remains at a low level after the controller stops working.
·VCC (pin 8): bias power supply access terminal. In order to absorb current spikes, this terminal should be externally connected to a filter capacitor.

2.3 Rated parameters

For ease of comparison, the rated parameters of TDA4862 and TDA4863 are listed in Table 2.

[page]2.4 Main electrical parameters

For easy comparison, the main electrical parameters of TDA4862 and TDA4863 are listed in Table 3.
Table 3 Comparison of main electrical parameters of TDA4862 and TDA4863

Note: (1) Unless otherwise specified, the test conditions are: -40℃≤TA≤150℃; VCC＝12V (TDA4862), VCC＝14.5V (TDA4863)

3. Working Principle

TDA4862 and TDA4863 both integrate precision trimming reference power supply, broadband voltage amplifier, overvoltage regulator, single quadrant multiplier, current detection comparator, zero current detector, PWM latch, restart timer, high current totem pole output circuit and undervoltage lockout circuit. Their principle block diagrams are shown in Figure 2 and Figure 3 respectively.
1. Voltage Amplifier
The gain bandwidth of the voltage amplifier in TDA4862 is 0.8MHz, and the phase margin reaches 80°. The non-inverting input of the voltage amplifier is used as the reference signal input terminal and is internally clamped at 2.5V, while its inverting input terminal is connected to the output terminal of the pre-converter through a resistor divider to detect the output voltage. A capacitor is connected between the output and inverting input of the voltage amplifier to form a feedback integration network. The bandwidth of the feedback network should generally be lower than 20Hz, which can effectively suppress the second harmonic in the input rectifier voltage ripple. In order to keep the output voltage stable, the output signal of the voltage amplifier is directly input into the multiplier to obtain the programming signal of the current detection comparator.
The gain bandwidth of the voltage amplifier in TDA4863 is increased to 3MHz, and a prohibition circuit is added. When the voltage on pin 1 of TDA4863 is lower than 0.2V, or the voltage on pin 2 is lower than 2.2V, the drive output circuit is prohibited.
2. Overvoltage regulator
The feedback integration network of the voltage amplifier has no effect on the sudden change of output voltage. The sudden change of output voltage usually occurs when the system starts, the load drops, or the arc discharge at the output end. The above situation will introduce a current spike at the input of the voltage amplifier, while the differential input voltage of the voltage amplifier remains zero. As a result, the current spike signal flows into the output of the voltage amplifier through the feedback capacitor, causing the output signal of the multiplier to drop.
3. Multiplier
The multiplier is the core component in the controller. The multiplier controls the drive output circuit according to the DC output voltage and the AC half-sine wave input voltage. The dynamic range linearity of the two input terminals of the multiplier is very good, where MULTIN (pin 3) is 0V~4V, and the voltage amplifier output terminal (pin 2) is 2.5V~4V. The output signal of the multiplier is clamped at 1.3V, which can effectively prevent the boost power MOSFET from working in a critical state when the system starts.
4. Current detection comparator and RS latch
The output signal of the multiplier is compared with the current detection signal to obtain the programming control signal of the drive output circuit. In order to ensure that there is only one drive pulse signal on the drive output terminal in a given cycle, an RS latch is added inside the controller. The output signal of the multiplier and the current detection threshold are both clamped at 1.3V, which can effectively prevent the boost power MOSFET from working in a critical state when the system starts. In addition, in order to prevent the input of negative pulse signals, a current source is added inside the controller. When the potential on pin 4 is lower than the ground potential, the current source will provide a sink current to pin 4. At the same time, the RC filter network integrated in the controller can effectively reduce the turn-on peak current.
The TDA4863 has an internal rising edge blanking circuit, which delays the turn-on current peak signal of the boost power MOSFET for a period of time, and its typical value is usually 200ns.

[page]5. Zero current detector

The zero current detector monitors the inductor current through the auxiliary winding on the boost inductor. When the inductor current passes through zero, it enters the next conduction cycle, so that the reverse recovery loss of the boost diode will be greatly reduced. When the voltage on the voltage divider resistor reaches the multiplier output threshold, the boost power MOSFET is turned off. Therefore, the boost current waveform is a continuous triangular wave with no dead zone interval between the waveforms. In this way, due to the continuous AC input line current, the peak switch current is limited to twice the average input current. To prevent false triggering, the zero current detector adopts a Schmitt trigger structure. The hysteresis voltage of the zero current detector in TDA4862 is 0.6V, while the hysteresis voltage of the zero current detector in TDA4862 is 0.5V. The built-in 5V clamp circuit can provide overvoltage protection for the zero current detector input, and the built-in 0.6V clamp circuit can effectively prevent base injection. In addition, a current limiting resistor must be connected in series with the auxiliary winding to prevent the clamp circuit from being damaged due to overcurrent.

6. Restart timer
If the driver output is still off 150μs after the inductor current reaches zero, the restart timer restarts the controller. Since the restart timer is integrated inside the controller, no oscillator is required.
7. Undervoltage lockout circuit
When the voltage on VCC (pin 8) exceeds the upper threshold, the undervoltage lockout circuit activates the driver output circuit. When the voltage on VCC (pin 8) is lower than the lower threshold, the undervoltage lockout circuit shuts down the driver output circuit. In standby mode, the typical bias current of TDA4862 is 75μA, and the bias current of TDA4863 is less than 100μA. To prevent the controller from being damaged by overvoltage, a built-in ground clamp circuit is added to VCC. The startup current is provided by an external startup resistor and energy storage capacitor.
8. Driver output circuit
The built-in totem pole driver output circuit of TDA4862 and TDA4863 can directly drive power MOSFET. When the controller is in standby mode, the protection circuit inside the controller is activated to ensure that the boost power MOSFET is reliably turned off. The drive output circuit of TDA4862 and TDA4863 is optimized for high-speed operation to minimize the on-state overlap current. In addition, the two 4Ω resistors connected in series with the current sink output transistor and the current pull output transistor can also effectively reduce the on-state overlap current.

4. Typical Applications

(1) The circuit schematic of the 110W wide input power factor pre-converter controlled by TDA4862 is shown in Figure 4.
(2) The circuit schematic of the power factor pre-converter in the 70W electronic ballast controlled by TDA4863 is shown in Figure 5.

Reference address：High Power Factor Controller TDA4862/63 and Its Application

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