Holtek HT45F0058 User manual

Low Component Cost Single Tube Induction Cooker
WAS-2041EN V1.00 1 / 19 February 25, 2021
Low Component Cost Single Tube
Induction Cooker
D/N: WAS-2041EN
Introduction
A traditional kitchen stove heats foods over an open flame while the induction cooker utilises an
electromagnetic induction method to implement a heating function. In this way foods are cooked
by the heat of the cookware itself. Compared to the open flame heating method, an induction cooker
can increase the heating efficiency by 90%. As a safety feature, the induction cooker will be
automatically shut off if the cookware has been removed for a certain period of time. During
cooking, the cooktop surface temperature is much lower than a traditional kitchen stove and in
addition, the induction cooker and cookware are more easily cleaned than a traditional stove.
A traditional single-tube induction cooker pursues a higher power, however in an IGBT resonance
circuit the reverse interference signal is also increased. The traditional way to solve this is to improve
the component specifications to enhance the induction cooker EMI circuit reverse interference signal
filtering capabilities. This reference design utilises a frequency jittering function to adjust the induction
cooker IGBT switching frequency, thus effectively decreasing the reverse voltage generated due to the
induction cooker IGBT switching as well as reducing the EMI CE conducted interference. In this way,
a lower component cost EMI circuit solution is provided. As the HT45F0058 includes an integrated
hardware frequency jittering circuit, this can effectively reduce the software load when compared with
the method whereby a software frequency jittering function is used.
Figure 1. Application Block Diagram

Low Component Cost Single Tube Induction Cooker
WAS-2041EN V1.00 2 / 19 February 25, 2021
Application Areas
Induction cookers, IH rice cookers, IH milk frothers.
Solution Feature
1. Dedicated hardware for frequency jittering: reduced software load, higher precision control.
If a software frequency jittering function is used, the software will occupy a section of the
program space and the CPU resources in order to achieve precise control. However, this
generally fails to obtain good control effects in actual product development due to software
resource limitations. This solution provides a PPG hardware frequency jittering circuit, which
uses a zero-crossing comparator to trigger a timer, the PPG width will be changed by
hardware at corresponding time points, which will eliminate the need to have frequency
jittering software. In this way, good control can be ensured and in addition, the software
execution time and program space requirements can be reduced. Using this method,
development difficulties can be reduced and the development time can be shortened.
2. Lower component costs: the MCU includes several integrated comparators and an operational
amplifier and the frequency jittering can reduce the component specifications.
The HT45F0058 includes several integrated comparators and an operational amplifier which
can be used for induction cooker over voltage and over current protection. In addition to
reduced external components, the PCB layout is also simplified. Enabling the hardware
frequency jittering function when the induction cooker operates at its maximum power can
effectively reduce the IGBT reverse voltage and the EMI conducted interference. As a result,
the IGBT component can be selected to have a lower voltage-resistant specification and the
safety capacitors can also select a lower capacitance value specification.
Operating Principles
By using a rectifier circuit in the induction cooker, the 50/60Hz alternating current can be converted
to direct current, which will pass through the resonance circuit and the IGBT switching circuit and
then be converted to a 20~35kHz high-frequency voltage. The high voltage results in a high-speed
varying current on the induction cooker coil panel which then generates a high speed varying
magnetic field. The magnetic field lines pass through the metal cookware on the cooktop surface
and generate eddy currents on the bottom of the metal cookware due to electromagnetic induction.
It is this which implements the heating function. The principle diagram is shown in Figure 2.
Cookware
Eddy Current
Eddy CurrentMagnetic Field Line
Cooktop Surface
Figure 2. Induction Cooker Heating Principle

Low Component Cost Single Tube Induction Cooker
WAS-2041EN V1.00 3 / 19 February 25, 2021
When the induction cooker operates at higher power levels of more than 1600W, the Holtek low
EMI component induction cooker solution can change the induction cooker IGBT resonance circuit
switching frequency using a frequency jittering function. As a result, when it is close to the peak
value of the mains voltage at 90 degrees, the IGBT VCE voltage can be effectively reduced as shown
in Figure 3. In addition, the higher electromagnetic interference signal energy will be dispersed into
different frequency spectrums, thus increasing the EMI CE conducted test margin.
Figure 3. Frequency Jittering Waveform
Functional Description
Solution Features
Input voltage range: AC 150V~265V 50/60Hz
Standby power consumption: < 5W
Communication interface: I2C – the power heating board is the software emulated master while
the touch & display board is the hardware circuit slave
Heating power: 100W~2000W (>1000W: continuous heating is used; <1000W: intermittent
heating is used.)
Protection functions: over/under voltage protection, over current protection, cooktop surface
overheating protection, IGBT overheating protection, surge voltage protection
EMI test: CE conducted interference test margin (2000W): > 2.82dB (avg.)
DP power interference test margin (2000W): > 10dB
Solution Function
An induction cooker solution is shown in Figure 4. This solution is suitable for general household
and commercial small hot pot cooking. The induction cooker supports multiple cooking modes,
such as fast heating, slow heating, soup, steam, porridge, hot pot and super high heating. The
differences between these modes are in the different heating power levels, time settings and
temperature control.

Low Component Cost Single Tube Induction Cooker
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Table 4. Induction Cooker
Operation Description
After the power cord is plugged in, the induction cooker enters the standby mode in which the fan
remains off, the buzzer sounds once and the 7-segment display and LEDs are all on and flashing.
After this, the “on/off” LED button on the control panel starts to flash, indicating that the induction
cooker initialisation has been completed. After pressing the “on/off” button, the LEDs will remain
on and the panel displays “----” waiting for further operations. When an error occurs, the display
area will display an error code.
Functional Key
Description
Pause Stop the current cooking mode, press again to resume the cooking mode
Smart
Press this button to switch between the following modes.
Fast heating mode: 100W~2000W adjustable power
>1000W: continuous heating is used; <1000W: intermittent heating is used.
Slow heating mode: 100W / 300W / 600W adjustable power
Soup mode: auto-adjustable power, use the time setting to setup a heating time,
ranging from 10 to 240 minutes in 10-minute increments.
Steam mode: auto-adjustable power, use the time setting to setup a heating
time, ranging from 10 to 240 minutes in 10-minute increments.
Porridge mode: The heating temperature in the pot can be adjusted, ranging
from 60℃ to 240℃ in 20°C increments.
Hot Pot 100W~2000W adjustable power
>1000W: continuous heating is used; <1000W: intermittent heating is used.
Super High Heating
2000W output power
Table 1. Solution Function Table
Error
Code Description
Error
Code
Description
E0
No cookware: Triggered when no cookware
is detected or the cookware is outside the
valid cooking zone.
E3
IGBT overheating: Triggered when the NTC
detected temperature is higher than 110℃
(±10℃)
E4
Triggered when an IGBT NTC open circuit
or short circuit condition occurs (2 minutes
for pre-heating is required)
E5
Cooktop surface overheating: Triggered when
the NTC detected temperature is higher than
the setup value of 160℃ (±10℃)
E6
Triggered when a cooktop surface NTC open
circuit or short circuit condition occurs (2
minutes for pre-heating is required)
E7
Mains supply over current: Triggered when
the A/D sampled current value is higher than
the setup value of 10A (±1A)
E8
Mains supply over voltage: Triggered when
the A/D sampled voltage value is higher
than the setup value of 265V(±10V)
E9
Mains supply under voltage: Triggered when
the voltage supply is lower than the setup
value of 150V (±10V)
EA
Communication failure: Triggered when an
I2C communication is interrupted or a
communication error occurs
Table 2. Induction Cooker Error Code Introduction

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Reference Design Description
The induction cooker can be divided into two parts, the power heating board and the touch & display
board. The power heating board contains the complete system power supply for the induction
cooker as well as the heating power control. The selection of the heating power and the induction
cooker on/off state on the power heating board are adjusted by the current heating power and other
settings on the touch & display board obtained via the I2C communication interface. The touch &
display board uses touch keys and LED display functions to provide a human-machine interface
(HMI) control. The touch keys can be used to select the desired operating mode while the LED
display function displays the current selected operating mode and power setting. The induction
cooker function error is also displayed on the touch & display board. In this solution, when the
induction cooker operates at a high power level of 1600W~2000W, the IGBT switching frequency
can be adjusted by a frequency jittering function thus reducing the maximum reverse voltage across
the IGBT VCE and the EMI conducted interference.
Hardware Description
1
5
23
8
10
11
4
7
6
9
Figure 5. Power Heating Board Schematic Diagram
The AC supply for the power heating board is divided into two paths after passing through the EMI
circuit. This is used as the heating main power for the switching power supply circuit(11) and the
resonance circuit(2). The switching power supply circuit(11) outputs two kinds of power supplies,
+18V and +5V. The +18V power is supplied to the buzzer & fan control circuit(4) and the IGBT
driving circuit(3). The +5V power is supplied to the HT45F0058 peripherals such as the cooktop
surface overheating protection circuit(6), IGBT overheating protection circuit(7) and the
communication circuit(9).

Low Component Cost Single Tube Induction Cooker
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The induction cooker power control is implemented depending upon the current detection circuit(5)
and the voltage detection circuit(10). These two circuits are used to detect the present operating
current value and the voltage value, which are used to calculate the present power. The system will
determine whether to increase or decrease the IGBT on-time to adjust the power according to the
present operating power. The measured current and voltage values are also used as the reference
source for the over/under voltage protection and for the over current protection functions.
In addition to the over/under voltage protection and over current protection functions, this solution
also contains a surge voltage protection circuit(8), a cooktop surface overheating protection circuit(6)
and an IGBT overheating protection circuit(7), etc. When any of the above protection functions are
triggered during induction cooker operation, the system determines whether to reduce power or stop
heating for safety reasons.
Touch & display board: The power heating board provides the power supply to the touch & display
board via the communication circuit. This voltage supply is regulated to a 5V voltage output by a
voltage regulation filtering circuit and is supplied as the touch & display board main power. The
LED display circuit displays the current induction cooker operating mode and function. The touch
keys are provided as a human-machine operating interface, with which functions can be selected.
The induction cooker will then control the power heating board operation according to the selected
function.
LED display circuit
Buzzer Control Circuit
(N.C.)
Communication
circuit
Voltage regulation
filtering circuit
Touch key circuit
Figure 6. Touch & Display Board Schematic Diagram

Low Component Cost Single Tube Induction Cooker
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Layout and Hardware Considerations
There are some important considerations for the power heating board.
1. The filter capacitors next to the MCU should be located as close to VDD and VSS as possible
and the ground of the peripheral circuit should be a single point grounded to the source capacitor
ground. The resonance circuit ground should be separated from other peripherals to avoid the
IGBT switching interference signal influencing other peripherals. Also ensure that the routes go
through a voltage regulation filtering capacitor to filter out any noise.
2. Routes from the bridge rectifier to resonance circuit should be widened as these routes carry
larger currents. The resonance capacitor should be as close as possible to the induction cooker
resonance coil.
3. Routing which is close to the high power area and the low power zone should be separated via
the KEEPOUT layer.
4. The IGBT E pin and the ground of the bridge rectifier IC should be widened and a single point
connected via a constantan wire, which is then single point routed to the current detection circuit.
Figure 7. Power Heating Board PCB
There are some considerations for the Touch MCU BS86D12C on the touch & display board.
1. The filter capacitors next to the MCU should be located as close to VDD and VSS as possible.
2. When there are multiple touch keys on the PCB, the MCU should be located to the center position
among these touch keys, thus shortening the route to reduce any effects of interference. Using
capacitors between the MCU corresponding KEY pins and VSS is an effective method of adjusting
the touch sensitivity. Wires can be routed from the MCU to the KEY pins on the copper floor to
reduce any interference on the touch keys caused by signal wires. It should be noted that any touch
key routing should be located as far as possible from the high frequency signal paths.
Figure 8. Touch & Display Board PCB

Low Component Cost Single Tube Induction Cooker
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PCB BOM Table
Table 3. Power Heating Board PCB BOM Ta b le

Low Component Cost Single Tube Induction Cooker
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Table 4. Touch & Display Board PCB BOM Table
Software Description
Software Resource Utilisation Introduction
HT45F0058 - Power Heating Board
BS86D12C - Touch & Display Board
V
DD
5.0V
5.0V
Oscillators
16MHz
8MHz
ROM
Uses 2868×16, occupancy rate: 70%
Uses 3043×16, occupancy rate: 37%
RAM
Uses 153×8, occupancy rate: 59%
Uses 307×16, occupancy rate: 59%
Stack
Uses 4 levels
Uses 4 levels
Timer
Uses TM(0~2)
Uses CTM0, Time Base 0
Other
Peripherals
1. ADC - AN1、AN3、AN4、AN5 for mains
supply, current and temperature measurement
2. PPG - IGBT switching signal source
3. CMP0, CMP1, CMP2, CMP3 used for resonance
circuit and induction cooker protections
4. OPA - current signal amplification
5. OVP - mains supply AC zero-crossing detection
6. PCK - passive buzzer signal source
7. I/Os - I2C Master end emulation
1. Touch Keys (KEY1~KEY8)
2. I2C
3. I/Os - for 7-segment display and
LED display
Table 5. Software Resource Utilisation
Power Heating Board Main Program Flowchart Description
As shown in Figure 9, the power heating board main program first executes initialisation, which
includes the I/O port settings related to the induction cooker register functions, power calculation
curves, etc. After initialisation, the voltage, current, IGBT temperature and cooktop surface
temperature are measured. Protection mechanisms will be triggered if the measurement results
exceed the limit range, then the corresponding flags will be set high, the corresponding error codes
will be stored into the communication memory and be sent to the touch & display board in the next
communication. The induction cooker main function control includes protection mechanisms, I2C
communication, power adjustment, etc.

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Comparator hardware protection interrupt: The surge voltage protection and IGBT reverse voltage
protection functions are implemented by hardware for a faster response speed. When these
protections are triggered, the system will turn off the heating function or reduce the heating power
first, further processing will be executed by software interrupt routines. If surge voltage protection
is triggered, the induction cooker heating function will be turned off to protect the induction cooker
from damage. If an IGBT reverse voltage protection is triggered, the induction cooker power will
be reduced by hardware to avoid the IGBT from being damaged.
Set high the corresponding protection
flags / store the error codes into the
communication memory
Measure the voltage (Mains supply),
current, IGBT temperature, cooktop
surface temperature
Measurement results trigger
the protection mechanism?
Induction cooker main
function control
N
System setting
initialis atio n
Start
CMP: surge voltage/IGBT over
voltage protection interr upt
Comparator
hardware protection
interrupt
Y
Figure 9. Power Heating Board Main Program Flowchart
Induction Cooker Main Function Control Flowchart Description
As shown in Figure 10, the induction cooker main function control flowchart executes specific
functions in several fixed periods. Over current protection detection, IGBT overheating protection
detection, NTC detection and protection release, etc., are executed every 1s. The I2C
communication, cookware detection and induction cooker power adjustment are executed every
100ms. The induction cooker On/Off and power setting, cookware removal detection as well as I2C
communication time-out processing are executed every 20ms. The system will determine if the time
has reached a value of 1s, 100ms and 20ms respectively every 1ms and then set high any
corresponding flags. The corresponding functions will be executed according to these flags in the
next process.
The system determines every second whether a mains supply over voltage or under voltage
condition occurs, whether an over current condition occurs and whether the IGBT temperature and
cooktop surface temperature requiring protection. It will then execute the corresponding protection
functions, such as adjusting the power or turning off the induction cooker heating function. For the