RM62 1 has built-in triangular wave generator, square wave forming, frequency tracking, phase compensation, waveform shaping, IGBT driving, high voltage limiting, high voltage protection, surge protection, power supply voltage detection, current detection and other circuits. Its internal block diagram is shown in Figure 2, and its main features are as follows:
The chip adopts TTL bipolar process, and has a precision operational amplifier with 100 times and several ultra-high-speed voltage comparators, which has strong anti-electromagnetic interference ability. Micro power consumption, the working current is not more than 15mA, and the static current is about1ma; ; Adopting special driving circuit for IGBT tube, IGBT tube has low working temperature and high reliability; The minimum continuous output power can be as low as 300W, and the maximum output power can reach 2600 W；; Simple circuit, few peripheral circuit elements, convenient circuit layout and little interference; Strong compatibility, can be used with multi-brand and multi-model microcomputer chips (MCU), and is convenient for maintenance and modification.
Since RM62 1A integrates the circuits of oscillation, comparative amplification and driving required by the induction cooker, the circuit of the induction cooker using this chip has few peripheral components and simple circuit. Its typical application circuit is shown in Figure 3, and the specific pin functions are as follows:
① Pin is the input end of power grid voltage detection and power grid surge (pulse) detection. Changing the capacity of external capacitor C5 can change the sensitivity of power grid surge detection. Changing the resistance ratio of external resistors R2 and R3 can change the output voltage of pin ⑩ and affect the voltage amplitude obtained by detecting power grid surge.
Pins ② and ③ are the input terminals of power phase sampling and high voltage feedback sampling respectively. Generally, under static state, the voltage at the foot ③ is 0.2V~0.5V higher than that at the foot ②.
In addition, a neutralization capacitor C 12 must be bridged between pins ② and ③ to eliminate self-excited interference. If the capacity of C 12 is too small, it will affect the high-voltage limit point and high-voltage protection point, so 470pF is generally selected. By changing the resistance ratio of external resistors R 14, R 15 and R 12, the high voltage limit and high voltage protection point can be changed.
④ Foot: Grounding.
⑤ Pin: Current sampling input. This terminal is externally connected with Kangtong copper wire resistor RJ through resistor R 10, and the voltage at both ends of RJ is used as the basis for current detection.
RJ is installed between the negative terminal of the high-voltage filter capacitor C2 and the negative terminal of the rectifier full bridge D 15, and its resistance value is 0.005 Ω ~ 0.01Ω.
⑥ Power supply terminal with pin of+18V. In order to drive IGBT normally, the power supply voltage of 18V should be neither too low nor too high, and its range is 15V ~ 19V.
⑦ Pin is a +5V reference voltage input terminal. Because this pin voltage will affect the high voltage limit and high voltage protection point of IC internal circuit, it is required that the 5V power supply is stable and the error is within 0.1V.
Pin tube is the driving pulse output end of IGBT tube, and is connected with the grid (G) of IGBT tube through resistor R8. The pulse waveform output by this pin is shown in Figure 4, and the high-level voltage value is VCC-0.7V, at this time, the IGBT tube is turned on; When the low-level voltage value is lower than 0.3V, the IGBT tube is turned off. The rising edge of the pulse is 300 30 nanoseconds and the falling edge is 250 25 nanoseconds.
Pet-name ruby pin is the current detection output terminal, and the output voltage at a certain moment is equal to 100 times the product of the working current of the whole machine (unit A) and the resistance value of Kang copper wire (unit ω). For example, at a certain moment, the current of the whole induction cooker is 10A, and the resistance value of the used Kang copper wire resistor is 0.0 1ω, then the pin 9 outputs voltage. If the component parameters in Figure 3 are used, the specific voltage value of pin 9 is shown in Figure 3.
Attending pin is the output of power supply voltage detection. The voltage value of this pin changes with the change of power supply voltage. If the component parameters in Figure 3 are used, the specific voltage value of pin 10 is shown in Figure 3.
1 1 and 12 pins are triangular wave forming terminals, and these two pins indirectly have a time constant setting capacitor C8(2200pF).
Pin 13 is an interrupt output. When the gate voltage appears instantaneous peak high voltage, or the voltage applied to the C electrode of IGBT tube is too high, this pin outputs low level, and at the same time, the driving pulse output of pin 8 in IC is turned off.
The 15 pin is the turn-off delay terminal, and its delay time is determined by the capacity of the external capacitor C 10.
The 14 pin is the switch control input, which is turned off at low level and turned on at high level. It should be noted that a certain voltage needs to be supplied to the 16 pin before starting. In addition, after the interrupt signal is output at the 13 pin, a low-level turn-off signal should be added at this pin, and it should be restarted after the voltage at the 13 pin returns to normal.
16 pin is the input of PWM power control signal. The higher the voltage of this pin, the greater the power of the whole machine. On the contrary, the smaller the power of the whole machine.